spanish-quizzer

chai.js (349596B)

---

 (function(f){if(typeof exports==="object"&&typeof module!=="undefined"){module.exports=f()}else if(typeof define==="function"&&define.amd){define([],f)}else{var g;if(typeof window!=="undefined"){g=window}else if(typeof global!=="undefined"){g=global}else if(typeof self!=="undefined"){g=self}else{g=this}g.chai = f()}})(function(){var define,module,exports;return (function(){function r(e,n,t){function o(i,f){if(!n[i]){if(!e[i]){var c="function"==typeof require&&require;if(!f&&c)return c(i,!0);if(u)return u(i,!0);var a=new Error("Cannot find module '"+i+"'");throw a.code="MODULE_NOT_FOUND",a}var p=n[i]={exports:{}};e[i][0].call(p.exports,function(r){var n=e[i][1][r];return o(n||r)},p,p.exports,r,e,n,t)}return n[i].exports}for(var u="function"==typeof require&&require,i=0;i<t.length;i++)o(t[i]);return o}return r})()({1:[function(require,module,exports){
 module.exports = require('./lib/chai');
 
 },{"./lib/chai":2}],2:[function(require,module,exports){
 /*!
  * chai
  * Copyright(c) 2011-2014 Jake Luer <jake@alogicalparadox.com>
  * MIT Licensed
  */
 
 var used = [];
 
 /*!
  * Chai version
  */
 
 exports.version = '4.3.3';
 
 /*!
  * Assertion Error
  */
 
 exports.AssertionError = require('assertion-error');
 
 /*!
  * Utils for plugins (not exported)
  */
 
 var util = require('./chai/utils');
 
 /**
  * # .use(function)
  *
  * Provides a way to extend the internals of Chai.
  *
  * @param {Function}
  * @returns {this} for chaining
  * @api public
  */
 
 exports.use = function (fn) {
   if (!~used.indexOf(fn)) {
     fn(exports, util);
     used.push(fn);
   }
 
   return exports;
 };
 
 /*!
  * Utility Functions
  */
 
 exports.util = util;
 
 /*!
  * Configuration
  */
 
 var config = require('./chai/config');
 exports.config = config;
 
 /*!
  * Primary `Assertion` prototype
  */
 
 var assertion = require('./chai/assertion');
 exports.use(assertion);
 
 /*!
  * Core Assertions
  */
 
 var core = require('./chai/core/assertions');
 exports.use(core);
 
 /*!
  * Expect interface
  */
 
 var expect = require('./chai/interface/expect');
 exports.use(expect);
 
 /*!
  * Should interface
  */
 
 var should = require('./chai/interface/should');
 exports.use(should);
 
 /*!
  * Assert interface
  */
 
 var assert = require('./chai/interface/assert');
 exports.use(assert);
 
 },{"./chai/assertion":3,"./chai/config":4,"./chai/core/assertions":5,"./chai/interface/assert":6,"./chai/interface/expect":7,"./chai/interface/should":8,"./chai/utils":23,"assertion-error":34}],3:[function(require,module,exports){
 /*!
  * chai
  * http://chaijs.com
  * Copyright(c) 2011-2014 Jake Luer <jake@alogicalparadox.com>
  * MIT Licensed
  */
 
 var config = require('./config');
 
 module.exports = function (_chai, util) {
   /*!
    * Module dependencies.
    */
 
   var AssertionError = _chai.AssertionError
     , flag = util.flag;
 
   /*!
    * Module export.
    */
 
   _chai.Assertion = Assertion;
 
   /*!
    * Assertion Constructor
    *
    * Creates object for chaining.
    *
    * `Assertion` objects contain metadata in the form of flags. Three flags can
    * be assigned during instantiation by passing arguments to this constructor:
    *
    * - `object`: This flag contains the target of the assertion. For example, in
    *   the assertion `expect(numKittens).to.equal(7);`, the `object` flag will
    *   contain `numKittens` so that the `equal` assertion can reference it when
    *   needed.
    *
    * - `message`: This flag contains an optional custom error message to be
    *   prepended to the error message that's generated by the assertion when it
    *   fails.
    *
    * - `ssfi`: This flag stands for "start stack function indicator". It
    *   contains a function reference that serves as the starting point for
    *   removing frames from the stack trace of the error that's created by the
    *   assertion when it fails. The goal is to provide a cleaner stack trace to
    *   end users by removing Chai's internal functions. Note that it only works
    *   in environments that support `Error.captureStackTrace`, and only when
    *   `Chai.config.includeStack` hasn't been set to `false`.
    *
    * - `lockSsfi`: This flag controls whether or not the given `ssfi` flag
    *   should retain its current value, even as assertions are chained off of
    *   this object. This is usually set to `true` when creating a new assertion
    *   from within another assertion. It's also temporarily set to `true` before
    *   an overwritten assertion gets called by the overwriting assertion.
    *
    * @param {Mixed} obj target of the assertion
    * @param {String} msg (optional) custom error message
    * @param {Function} ssfi (optional) starting point for removing stack frames
    * @param {Boolean} lockSsfi (optional) whether or not the ssfi flag is locked
    * @api private
    */
 
   function Assertion (obj, msg, ssfi, lockSsfi) {
     flag(this, 'ssfi', ssfi || Assertion);
     flag(this, 'lockSsfi', lockSsfi);
     flag(this, 'object', obj);
     flag(this, 'message', msg);
 
     return util.proxify(this);
   }
 
   Object.defineProperty(Assertion, 'includeStack', {
     get: function() {
       console.warn('Assertion.includeStack is deprecated, use chai.config.includeStack instead.');
       return config.includeStack;
     },
     set: function(value) {
       console.warn('Assertion.includeStack is deprecated, use chai.config.includeStack instead.');
       config.includeStack = value;
     }
   });
 
   Object.defineProperty(Assertion, 'showDiff', {
     get: function() {
       console.warn('Assertion.showDiff is deprecated, use chai.config.showDiff instead.');
       return config.showDiff;
     },
     set: function(value) {
       console.warn('Assertion.showDiff is deprecated, use chai.config.showDiff instead.');
       config.showDiff = value;
     }
   });
 
   Assertion.addProperty = function (name, fn) {
     util.addProperty(this.prototype, name, fn);
   };
 
   Assertion.addMethod = function (name, fn) {
     util.addMethod(this.prototype, name, fn);
   };
 
   Assertion.addChainableMethod = function (name, fn, chainingBehavior) {
     util.addChainableMethod(this.prototype, name, fn, chainingBehavior);
   };
 
   Assertion.overwriteProperty = function (name, fn) {
     util.overwriteProperty(this.prototype, name, fn);
   };
 
   Assertion.overwriteMethod = function (name, fn) {
     util.overwriteMethod(this.prototype, name, fn);
   };
 
   Assertion.overwriteChainableMethod = function (name, fn, chainingBehavior) {
     util.overwriteChainableMethod(this.prototype, name, fn, chainingBehavior);
   };
 
   /**
    * ### .assert(expression, message, negateMessage, expected, actual, showDiff)
    *
    * Executes an expression and check expectations. Throws AssertionError for reporting if test doesn't pass.
    *
    * @name assert
    * @param {Philosophical} expression to be tested
    * @param {String|Function} message or function that returns message to display if expression fails
    * @param {String|Function} negatedMessage or function that returns negatedMessage to display if negated expression fails
    * @param {Mixed} expected value (remember to check for negation)
    * @param {Mixed} actual (optional) will default to `this.obj`
    * @param {Boolean} showDiff (optional) when set to `true`, assert will display a diff in addition to the message if expression fails
    * @api private
    */
 
   Assertion.prototype.assert = function (expr, msg, negateMsg, expected, _actual, showDiff) {
     var ok = util.test(this, arguments);
     if (false !== showDiff) showDiff = true;
     if (undefined === expected && undefined === _actual) showDiff = false;
     if (true !== config.showDiff) showDiff = false;
 
     if (!ok) {
       msg = util.getMessage(this, arguments);
       var actual = util.getActual(this, arguments);
       var assertionErrorObjectProperties = {
           actual: actual
         , expected: expected
         , showDiff: showDiff
       };
 
       var operator = util.getOperator(this, arguments);
       if (operator) {
         assertionErrorObjectProperties.operator = operator;
       }
 
       throw new AssertionError(
         msg,
         assertionErrorObjectProperties,
         (config.includeStack) ? this.assert : flag(this, 'ssfi'));
     }
   };
 
   /*!
    * ### ._obj
    *
    * Quick reference to stored `actual` value for plugin developers.
    *
    * @api private
    */
 
   Object.defineProperty(Assertion.prototype, '_obj',
     { get: function () {
         return flag(this, 'object');
       }
     , set: function (val) {
         flag(this, 'object', val);
       }
   });
 };
 
 },{"./config":4}],4:[function(require,module,exports){
 module.exports = {
 
   /**
    * ### config.includeStack
    *
    * User configurable property, influences whether stack trace
    * is included in Assertion error message. Default of false
    * suppresses stack trace in the error message.
    *
    *     chai.config.includeStack = true;  // enable stack on error
    *
    * @param {Boolean}
    * @api public
    */
 
   includeStack: false,
 
   /**
    * ### config.showDiff
    *
    * User configurable property, influences whether or not
    * the `showDiff` flag should be included in the thrown
    * AssertionErrors. `false` will always be `false`; `true`
    * will be true when the assertion has requested a diff
    * be shown.
    *
    * @param {Boolean}
    * @api public
    */
 
   showDiff: true,
 
   /**
    * ### config.truncateThreshold
    *
    * User configurable property, sets length threshold for actual and
    * expected values in assertion errors. If this threshold is exceeded, for
    * example for large data structures, the value is replaced with something
    * like `[ Array(3) ]` or `{ Object (prop1, prop2) }`.
    *
    * Set it to zero if you want to disable truncating altogether.
    *
    * This is especially userful when doing assertions on arrays: having this
    * set to a reasonable large value makes the failure messages readily
    * inspectable.
    *
    *     chai.config.truncateThreshold = 0;  // disable truncating
    *
    * @param {Number}
    * @api public
    */
 
   truncateThreshold: 40,
 
   /**
    * ### config.useProxy
    *
    * User configurable property, defines if chai will use a Proxy to throw
    * an error when a non-existent property is read, which protects users
    * from typos when using property-based assertions.
    *
    * Set it to false if you want to disable this feature.
    *
    *     chai.config.useProxy = false;  // disable use of Proxy
    *
    * This feature is automatically disabled regardless of this config value
    * in environments that don't support proxies.
    *
    * @param {Boolean}
    * @api public
    */
 
   useProxy: true,
 
   /**
    * ### config.proxyExcludedKeys
    *
    * User configurable property, defines which properties should be ignored
    * instead of throwing an error if they do not exist on the assertion.
    * This is only applied if the environment Chai is running in supports proxies and
    * if the `useProxy` configuration setting is enabled.
    * By default, `then` and `inspect` will not throw an error if they do not exist on the
    * assertion object because the `.inspect` property is read by `util.inspect` (for example, when
    * using `console.log` on the assertion object) and `.then` is necessary for promise type-checking.
    *
    *     // By default these keys will not throw an error if they do not exist on the assertion object
    *     chai.config.proxyExcludedKeys = ['then', 'inspect'];
    *
    * @param {Array}
    * @api public
    */
 
   proxyExcludedKeys: ['then', 'catch', 'inspect', 'toJSON']
 };
 
 },{}],5:[function(require,module,exports){
 /*!
  * chai
  * http://chaijs.com
  * Copyright(c) 2011-2014 Jake Luer <jake@alogicalparadox.com>
  * MIT Licensed
  */
 
 module.exports = function (chai, _) {
   var Assertion = chai.Assertion
     , AssertionError = chai.AssertionError
     , flag = _.flag;
 
   /**
    * ### Language Chains
    *
    * The following are provided as chainable getters to improve the readability
    * of your assertions.
    *
    * **Chains**
    *
    * - to
    * - be
    * - been
    * - is
    * - that
    * - which
    * - and
    * - has
    * - have
    * - with
    * - at
    * - of
    * - same
    * - but
    * - does
    * - still
    * - also
    *
    * @name language chains
    * @namespace BDD
    * @api public
    */
 
   [ 'to', 'be', 'been', 'is'
   , 'and', 'has', 'have', 'with'
   , 'that', 'which', 'at', 'of'
   , 'same', 'but', 'does', 'still', "also" ].forEach(function (chain) {
     Assertion.addProperty(chain);
   });
 
   /**
    * ### .not
    *
    * Negates all assertions that follow in the chain.
    *
    *     expect(function () {}).to.not.throw();
    *     expect({a: 1}).to.not.have.property('b');
    *     expect([1, 2]).to.be.an('array').that.does.not.include(3);
    *
    * Just because you can negate any assertion with `.not` doesn't mean you
    * should. With great power comes great responsibility. It's often best to
    * assert that the one expected output was produced, rather than asserting
    * that one of countless unexpected outputs wasn't produced. See individual
    * assertions for specific guidance.
    *
    *     expect(2).to.equal(2); // Recommended
    *     expect(2).to.not.equal(1); // Not recommended
    *
    * @name not
    * @namespace BDD
    * @api public
    */
 
   Assertion.addProperty('not', function () {
     flag(this, 'negate', true);
   });
 
   /**
    * ### .deep
    *
    * Causes all `.equal`, `.include`, `.members`, `.keys`, and `.property`
    * assertions that follow in the chain to use deep equality instead of strict
    * (`===`) equality. See the `deep-eql` project page for info on the deep
    * equality algorithm: https://github.com/chaijs/deep-eql.
    *
    *     // Target object deeply (but not strictly) equals `{a: 1}`
    *     expect({a: 1}).to.deep.equal({a: 1});
    *     expect({a: 1}).to.not.equal({a: 1});
    *
    *     // Target array deeply (but not strictly) includes `{a: 1}`
    *     expect([{a: 1}]).to.deep.include({a: 1});
    *     expect([{a: 1}]).to.not.include({a: 1});
    *
    *     // Target object deeply (but not strictly) includes `x: {a: 1}`
    *     expect({x: {a: 1}}).to.deep.include({x: {a: 1}});
    *     expect({x: {a: 1}}).to.not.include({x: {a: 1}});
    *
    *     // Target array deeply (but not strictly) has member `{a: 1}`
    *     expect([{a: 1}]).to.have.deep.members([{a: 1}]);
    *     expect([{a: 1}]).to.not.have.members([{a: 1}]);
    *
    *     // Target set deeply (but not strictly) has key `{a: 1}`
    *     expect(new Set([{a: 1}])).to.have.deep.keys([{a: 1}]);
    *     expect(new Set([{a: 1}])).to.not.have.keys([{a: 1}]);
    *
    *     // Target object deeply (but not strictly) has property `x: {a: 1}`
    *     expect({x: {a: 1}}).to.have.deep.property('x', {a: 1});
    *     expect({x: {a: 1}}).to.not.have.property('x', {a: 1});
    *
    * @name deep
    * @namespace BDD
    * @api public
    */
 
   Assertion.addProperty('deep', function () {
     flag(this, 'deep', true);
   });
 
   /**
    * ### .nested
    *
    * Enables dot- and bracket-notation in all `.property` and `.include`
    * assertions that follow in the chain.
    *
    *     expect({a: {b: ['x', 'y']}}).to.have.nested.property('a.b[1]');
    *     expect({a: {b: ['x', 'y']}}).to.nested.include({'a.b[1]': 'y'});
    *
    * If `.` or `[]` are part of an actual property name, they can be escaped by
    * adding two backslashes before them.
    *
    *     expect({'.a': {'[b]': 'x'}}).to.have.nested.property('\\.a.\\[b\\]');
    *     expect({'.a': {'[b]': 'x'}}).to.nested.include({'\\.a.\\[b\\]': 'x'});
    *
    * `.nested` cannot be combined with `.own`.
    *
    * @name nested
    * @namespace BDD
    * @api public
    */
 
   Assertion.addProperty('nested', function () {
     flag(this, 'nested', true);
   });
 
   /**
    * ### .own
    *
    * Causes all `.property` and `.include` assertions that follow in the chain
    * to ignore inherited properties.
    *
    *     Object.prototype.b = 2;
    *
    *     expect({a: 1}).to.have.own.property('a');
    *     expect({a: 1}).to.have.property('b');
    *     expect({a: 1}).to.not.have.own.property('b');
    *
    *     expect({a: 1}).to.own.include({a: 1});
    *     expect({a: 1}).to.include({b: 2}).but.not.own.include({b: 2});
    *
    * `.own` cannot be combined with `.nested`.
    *
    * @name own
    * @namespace BDD
    * @api public
    */
 
   Assertion.addProperty('own', function () {
     flag(this, 'own', true);
   });
 
   /**
    * ### .ordered
    *
    * Causes all `.members` assertions that follow in the chain to require that
    * members be in the same order.
    *
    *     expect([1, 2]).to.have.ordered.members([1, 2])
    *       .but.not.have.ordered.members([2, 1]);
    *
    * When `.include` and `.ordered` are combined, the ordering begins at the
    * start of both arrays.
    *
    *     expect([1, 2, 3]).to.include.ordered.members([1, 2])
    *       .but.not.include.ordered.members([2, 3]);
    *
    * @name ordered
    * @namespace BDD
    * @api public
    */
 
   Assertion.addProperty('ordered', function () {
     flag(this, 'ordered', true);
   });
 
   /**
    * ### .any
    *
    * Causes all `.keys` assertions that follow in the chain to only require that
    * the target have at least one of the given keys. This is the opposite of
    * `.all`, which requires that the target have all of the given keys.
    *
    *     expect({a: 1, b: 2}).to.not.have.any.keys('c', 'd');
    *
    * See the `.keys` doc for guidance on when to use `.any` or `.all`.
    *
    * @name any
    * @namespace BDD
    * @api public
    */
 
   Assertion.addProperty('any', function () {
     flag(this, 'any', true);
     flag(this, 'all', false);
   });
 
   /**
    * ### .all
    *
    * Causes all `.keys` assertions that follow in the chain to require that the
    * target have all of the given keys. This is the opposite of `.any`, which
    * only requires that the target have at least one of the given keys.
    *
    *     expect({a: 1, b: 2}).to.have.all.keys('a', 'b');
    *
    * Note that `.all` is used by default when neither `.all` nor `.any` are
    * added earlier in the chain. However, it's often best to add `.all` anyway
    * because it improves readability.
    *
    * See the `.keys` doc for guidance on when to use `.any` or `.all`.
    *
    * @name all
    * @namespace BDD
    * @api public
    */
 
   Assertion.addProperty('all', function () {
     flag(this, 'all', true);
     flag(this, 'any', false);
   });
 
   /**
    * ### .a(type[, msg])
    *
    * Asserts that the target's type is equal to the given string `type`. Types
    * are case insensitive. See the `type-detect` project page for info on the
    * type detection algorithm: https://github.com/chaijs/type-detect.
    *
    *     expect('foo').to.be.a('string');
    *     expect({a: 1}).to.be.an('object');
    *     expect(null).to.be.a('null');
    *     expect(undefined).to.be.an('undefined');
    *     expect(new Error).to.be.an('error');
    *     expect(Promise.resolve()).to.be.a('promise');
    *     expect(new Float32Array).to.be.a('float32array');
    *     expect(Symbol()).to.be.a('symbol');
    *
    * `.a` supports objects that have a custom type set via `Symbol.toStringTag`.
    *
    *     var myObj = {
    *       [Symbol.toStringTag]: 'myCustomType'
    *     };
    *
    *     expect(myObj).to.be.a('myCustomType').but.not.an('object');
    *
    * It's often best to use `.a` to check a target's type before making more
    * assertions on the same target. That way, you avoid unexpected behavior from
    * any assertion that does different things based on the target's type.
    *
    *     expect([1, 2, 3]).to.be.an('array').that.includes(2);
    *     expect([]).to.be.an('array').that.is.empty;
    *
    * Add `.not` earlier in the chain to negate `.a`. However, it's often best to
    * assert that the target is the expected type, rather than asserting that it
    * isn't one of many unexpected types.
    *
    *     expect('foo').to.be.a('string'); // Recommended
    *     expect('foo').to.not.be.an('array'); // Not recommended
    *
    * `.a` accepts an optional `msg` argument which is a custom error message to
    * show when the assertion fails. The message can also be given as the second
    * argument to `expect`.
    *
    *     expect(1).to.be.a('string', 'nooo why fail??');
    *     expect(1, 'nooo why fail??').to.be.a('string');
    *
    * `.a` can also be used as a language chain to improve the readability of
    * your assertions.
    *
    *     expect({b: 2}).to.have.a.property('b');
    *
    * The alias `.an` can be used interchangeably with `.a`.
    *
    * @name a
    * @alias an
    * @param {String} type
    * @param {String} msg _optional_
    * @namespace BDD
    * @api public
    */
 
   function an (type, msg) {
     if (msg) flag(this, 'message', msg);
     type = type.toLowerCase();
     var obj = flag(this, 'object')
       , article = ~[ 'a', 'e', 'i', 'o', 'u' ].indexOf(type.charAt(0)) ? 'an ' : 'a ';
 
     this.assert(
         type === _.type(obj).toLowerCase()
       , 'expected #{this} to be ' + article + type
       , 'expected #{this} not to be ' + article + type
     );
   }
 
   Assertion.addChainableMethod('an', an);
   Assertion.addChainableMethod('a', an);
 
   /**
    * ### .include(val[, msg])
    *
    * When the target is a string, `.include` asserts that the given string `val`
    * is a substring of the target.
    *
    *     expect('foobar').to.include('foo');
    *
    * When the target is an array, `.include` asserts that the given `val` is a
    * member of the target.
    *
    *     expect([1, 2, 3]).to.include(2);
    *
    * When the target is an object, `.include` asserts that the given object
    * `val`'s properties are a subset of the target's properties.
    *
    *     expect({a: 1, b: 2, c: 3}).to.include({a: 1, b: 2});
    *
    * When the target is a Set or WeakSet, `.include` asserts that the given `val` is a
    * member of the target. SameValueZero equality algorithm is used.
    *
    *     expect(new Set([1, 2])).to.include(2);
    *
    * When the target is a Map, `.include` asserts that the given `val` is one of
    * the values of the target. SameValueZero equality algorithm is used.
    *
    *     expect(new Map([['a', 1], ['b', 2]])).to.include(2);
    *
    * Because `.include` does different things based on the target's type, it's
    * important to check the target's type before using `.include`. See the `.a`
    * doc for info on testing a target's type.
    *
    *     expect([1, 2, 3]).to.be.an('array').that.includes(2);
    *
    * By default, strict (`===`) equality is used to compare array members and
    * object properties. Add `.deep` earlier in the chain to use deep equality
    * instead (WeakSet targets are not supported). See the `deep-eql` project
    * page for info on the deep equality algorithm: https://github.com/chaijs/deep-eql.
    *
    *     // Target array deeply (but not strictly) includes `{a: 1}`
    *     expect([{a: 1}]).to.deep.include({a: 1});
    *     expect([{a: 1}]).to.not.include({a: 1});
    *
    *     // Target object deeply (but not strictly) includes `x: {a: 1}`
    *     expect({x: {a: 1}}).to.deep.include({x: {a: 1}});
    *     expect({x: {a: 1}}).to.not.include({x: {a: 1}});
    *
    * By default, all of the target's properties are searched when working with
    * objects. This includes properties that are inherited and/or non-enumerable.
    * Add `.own` earlier in the chain to exclude the target's inherited
    * properties from the search.
    *
    *     Object.prototype.b = 2;
    *
    *     expect({a: 1}).to.own.include({a: 1});
    *     expect({a: 1}).to.include({b: 2}).but.not.own.include({b: 2});
    *
    * Note that a target object is always only searched for `val`'s own
    * enumerable properties.
    *
    * `.deep` and `.own` can be combined.
    *
    *     expect({a: {b: 2}}).to.deep.own.include({a: {b: 2}});
    *
    * Add `.nested` earlier in the chain to enable dot- and bracket-notation when
    * referencing nested properties.
    *
    *     expect({a: {b: ['x', 'y']}}).to.nested.include({'a.b[1]': 'y'});
    *
    * If `.` or `[]` are part of an actual property name, they can be escaped by
    * adding two backslashes before them.
    *
    *     expect({'.a': {'[b]': 2}}).to.nested.include({'\\.a.\\[b\\]': 2});
    *
    * `.deep` and `.nested` can be combined.
    *
    *     expect({a: {b: [{c: 3}]}}).to.deep.nested.include({'a.b[0]': {c: 3}});
    *
    * `.own` and `.nested` cannot be combined.
    *
    * Add `.not` earlier in the chain to negate `.include`.
    *
    *     expect('foobar').to.not.include('taco');
    *     expect([1, 2, 3]).to.not.include(4);
    *
    * However, it's dangerous to negate `.include` when the target is an object.
    * The problem is that it creates uncertain expectations by asserting that the
    * target object doesn't have all of `val`'s key/value pairs but may or may
    * not have some of them. It's often best to identify the exact output that's
    * expected, and then write an assertion that only accepts that exact output.
    *
    * When the target object isn't even expected to have `val`'s keys, it's
    * often best to assert exactly that.
    *
    *     expect({c: 3}).to.not.have.any.keys('a', 'b'); // Recommended
    *     expect({c: 3}).to.not.include({a: 1, b: 2}); // Not recommended
    *
    * When the target object is expected to have `val`'s keys, it's often best to
    * assert that each of the properties has its expected value, rather than
    * asserting that each property doesn't have one of many unexpected values.
    *
    *     expect({a: 3, b: 4}).to.include({a: 3, b: 4}); // Recommended
    *     expect({a: 3, b: 4}).to.not.include({a: 1, b: 2}); // Not recommended
    *
    * `.include` accepts an optional `msg` argument which is a custom error
    * message to show when the assertion fails. The message can also be given as
    * the second argument to `expect`.
    *
    *     expect([1, 2, 3]).to.include(4, 'nooo why fail??');
    *     expect([1, 2, 3], 'nooo why fail??').to.include(4);
    *
    * `.include` can also be used as a language chain, causing all `.members` and
    * `.keys` assertions that follow in the chain to require the target to be a
    * superset of the expected set, rather than an identical set. Note that
    * `.members` ignores duplicates in the subset when `.include` is added.
    *
    *     // Target object's keys are a superset of ['a', 'b'] but not identical
    *     expect({a: 1, b: 2, c: 3}).to.include.all.keys('a', 'b');
    *     expect({a: 1, b: 2, c: 3}).to.not.have.all.keys('a', 'b');
    *
    *     // Target array is a superset of [1, 2] but not identical
    *     expect([1, 2, 3]).to.include.members([1, 2]);
    *     expect([1, 2, 3]).to.not.have.members([1, 2]);
    *
    *     // Duplicates in the subset are ignored
    *     expect([1, 2, 3]).to.include.members([1, 2, 2, 2]);
    *
    * Note that adding `.any` earlier in the chain causes the `.keys` assertion
    * to ignore `.include`.
    *
    *     // Both assertions are identical
    *     expect({a: 1}).to.include.any.keys('a', 'b');
    *     expect({a: 1}).to.have.any.keys('a', 'b');
    *
    * The aliases `.includes`, `.contain`, and `.contains` can be used
    * interchangeably with `.include`.
    *
    * @name include
    * @alias contain
    * @alias includes
    * @alias contains
    * @param {Mixed} val
    * @param {String} msg _optional_
    * @namespace BDD
    * @api public
    */
 
   function SameValueZero(a, b) {
     return (_.isNaN(a) && _.isNaN(b)) || a === b;
   }
 
   function includeChainingBehavior () {
     flag(this, 'contains', true);
   }
 
   function include (val, msg) {
     if (msg) flag(this, 'message', msg);
 
     var obj = flag(this, 'object')
       , objType = _.type(obj).toLowerCase()
       , flagMsg = flag(this, 'message')
       , negate = flag(this, 'negate')
       , ssfi = flag(this, 'ssfi')
       , isDeep = flag(this, 'deep')
       , descriptor = isDeep ? 'deep ' : '';
 
     flagMsg = flagMsg ? flagMsg + ': ' : '';
 
     var included = false;
 
     switch (objType) {
       case 'string':
         included = obj.indexOf(val) !== -1;
         break;
 
       case 'weakset':
         if (isDeep) {
           throw new AssertionError(
             flagMsg + 'unable to use .deep.include with WeakSet',
             undefined,
             ssfi
           );
         }
 
         included = obj.has(val);
         break;
 
       case 'map':
         var isEql = isDeep ? _.eql : SameValueZero;
         obj.forEach(function (item) {
           included = included || isEql(item, val);
         });
         break;
 
       case 'set':
         if (isDeep) {
           obj.forEach(function (item) {
             included = included || _.eql(item, val);
           });
         } else {
           included = obj.has(val);
         }
         break;
 
       case 'array':
         if (isDeep) {
           included = obj.some(function (item) {
             return _.eql(item, val);
           })
         } else {
           included = obj.indexOf(val) !== -1;
         }
         break;
 
       default:
         // This block is for asserting a subset of properties in an object.
         // `_.expectTypes` isn't used here because `.include` should work with
         // objects with a custom `@@toStringTag`.
         if (val !== Object(val)) {
           throw new AssertionError(
             flagMsg + 'the given combination of arguments ('
             + objType + ' and '
             + _.type(val).toLowerCase() + ')'
             + ' is invalid for this assertion. '
             + 'You can use an array, a map, an object, a set, a string, '
             + 'or a weakset instead of a '
             + _.type(val).toLowerCase(),
             undefined,
             ssfi
           );
         }
 
         var props = Object.keys(val)
           , firstErr = null
           , numErrs = 0;
 
         props.forEach(function (prop) {
           var propAssertion = new Assertion(obj);
           _.transferFlags(this, propAssertion, true);
           flag(propAssertion, 'lockSsfi', true);
 
           if (!negate || props.length === 1) {
             propAssertion.property(prop, val[prop]);
             return;
           }
 
           try {
             propAssertion.property(prop, val[prop]);
           } catch (err) {
             if (!_.checkError.compatibleConstructor(err, AssertionError)) {
               throw err;
             }
             if (firstErr === null) firstErr = err;
             numErrs++;
           }
         }, this);
 
         // When validating .not.include with multiple properties, we only want
         // to throw an assertion error if all of the properties are included,
         // in which case we throw the first property assertion error that we
         // encountered.
         if (negate && props.length > 1 && numErrs === props.length) {
           throw firstErr;
         }
         return;
     }
 
     // Assert inclusion in collection or substring in a string.
     this.assert(
       included
       , 'expected #{this} to ' + descriptor + 'include ' + _.inspect(val)
       , 'expected #{this} to not ' + descriptor + 'include ' + _.inspect(val));
   }
 
   Assertion.addChainableMethod('include', include, includeChainingBehavior);
   Assertion.addChainableMethod('contain', include, includeChainingBehavior);
   Assertion.addChainableMethod('contains', include, includeChainingBehavior);
   Assertion.addChainableMethod('includes', include, includeChainingBehavior);
 
   /**
    * ### .ok
    *
    * Asserts that the target is a truthy value (considered `true` in boolean context).
    * However, it's often best to assert that the target is strictly (`===`) or
    * deeply equal to its expected value.
    *
    *     expect(1).to.equal(1); // Recommended
    *     expect(1).to.be.ok; // Not recommended
    *
    *     expect(true).to.be.true; // Recommended
    *     expect(true).to.be.ok; // Not recommended
    *
    * Add `.not` earlier in the chain to negate `.ok`.
    *
    *     expect(0).to.equal(0); // Recommended
    *     expect(0).to.not.be.ok; // Not recommended
    *
    *     expect(false).to.be.false; // Recommended
    *     expect(false).to.not.be.ok; // Not recommended
    *
    *     expect(null).to.be.null; // Recommended
    *     expect(null).to.not.be.ok; // Not recommended
    *
    *     expect(undefined).to.be.undefined; // Recommended
    *     expect(undefined).to.not.be.ok; // Not recommended
    *
    * A custom error message can be given as the second argument to `expect`.
    *
    *     expect(false, 'nooo why fail??').to.be.ok;
    *
    * @name ok
    * @namespace BDD
    * @api public
    */
 
   Assertion.addProperty('ok', function () {
     this.assert(
         flag(this, 'object')
       , 'expected #{this} to be truthy'
       , 'expected #{this} to be falsy');
   });
 
   /**
    * ### .true
    *
    * Asserts that the target is strictly (`===`) equal to `true`.
    *
    *     expect(true).to.be.true;
    *
    * Add `.not` earlier in the chain to negate `.true`. However, it's often best
    * to assert that the target is equal to its expected value, rather than not
    * equal to `true`.
    *
    *     expect(false).to.be.false; // Recommended
    *     expect(false).to.not.be.true; // Not recommended
    *
    *     expect(1).to.equal(1); // Recommended
    *     expect(1).to.not.be.true; // Not recommended
    *
    * A custom error message can be given as the second argument to `expect`.
    *
    *     expect(false, 'nooo why fail??').to.be.true;
    *
    * @name true
    * @namespace BDD
    * @api public
    */
 
   Assertion.addProperty('true', function () {
     this.assert(
         true === flag(this, 'object')
       , 'expected #{this} to be true'
       , 'expected #{this} to be false'
       , flag(this, 'negate') ? false : true
     );
   });
 
   /**
    * ### .false
    *
    * Asserts that the target is strictly (`===`) equal to `false`.
    *
    *     expect(false).to.be.false;
    *
    * Add `.not` earlier in the chain to negate `.false`. However, it's often
    * best to assert that the target is equal to its expected value, rather than
    * not equal to `false`.
    *
    *     expect(true).to.be.true; // Recommended
    *     expect(true).to.not.be.false; // Not recommended
    *
    *     expect(1).to.equal(1); // Recommended
    *     expect(1).to.not.be.false; // Not recommended
    *
    * A custom error message can be given as the second argument to `expect`.
    *
    *     expect(true, 'nooo why fail??').to.be.false;
    *
    * @name false
    * @namespace BDD
    * @api public
    */
 
   Assertion.addProperty('false', function () {
     this.assert(
         false === flag(this, 'object')
       , 'expected #{this} to be false'
       , 'expected #{this} to be true'
       , flag(this, 'negate') ? true : false
     );
   });
 
   /**
    * ### .null
    *
    * Asserts that the target is strictly (`===`) equal to `null`.
    *
    *     expect(null).to.be.null;
    *
    * Add `.not` earlier in the chain to negate `.null`. However, it's often best
    * to assert that the target is equal to its expected value, rather than not
    * equal to `null`.
    *
    *     expect(1).to.equal(1); // Recommended
    *     expect(1).to.not.be.null; // Not recommended
    *
    * A custom error message can be given as the second argument to `expect`.
    *
    *     expect(42, 'nooo why fail??').to.be.null;
    *
    * @name null
    * @namespace BDD
    * @api public
    */
 
   Assertion.addProperty('null', function () {
     this.assert(
         null === flag(this, 'object')
       , 'expected #{this} to be null'
       , 'expected #{this} not to be null'
     );
   });
 
   /**
    * ### .undefined
    *
    * Asserts that the target is strictly (`===`) equal to `undefined`.
    *
    *     expect(undefined).to.be.undefined;
    *
    * Add `.not` earlier in the chain to negate `.undefined`. However, it's often
    * best to assert that the target is equal to its expected value, rather than
    * not equal to `undefined`.
    *
    *     expect(1).to.equal(1); // Recommended
    *     expect(1).to.not.be.undefined; // Not recommended
    *
    * A custom error message can be given as the second argument to `expect`.
    *
    *     expect(42, 'nooo why fail??').to.be.undefined;
    *
    * @name undefined
    * @namespace BDD
    * @api public
    */
 
   Assertion.addProperty('undefined', function () {
     this.assert(
         undefined === flag(this, 'object')
       , 'expected #{this} to be undefined'
       , 'expected #{this} not to be undefined'
     );
   });
 
   /**
    * ### .NaN
    *
    * Asserts that the target is exactly `NaN`.
    *
    *     expect(NaN).to.be.NaN;
    *
    * Add `.not` earlier in the chain to negate `.NaN`. However, it's often best
    * to assert that the target is equal to its expected value, rather than not
    * equal to `NaN`.
    *
    *     expect('foo').to.equal('foo'); // Recommended
    *     expect('foo').to.not.be.NaN; // Not recommended
    *
    * A custom error message can be given as the second argument to `expect`.
    *
    *     expect(42, 'nooo why fail??').to.be.NaN;
    *
    * @name NaN
    * @namespace BDD
    * @api public
    */
 
   Assertion.addProperty('NaN', function () {
     this.assert(
         _.isNaN(flag(this, 'object'))
         , 'expected #{this} to be NaN'
         , 'expected #{this} not to be NaN'
     );
   });
 
   /**
    * ### .exist
    *
    * Asserts that the target is not strictly (`===`) equal to either `null` or
    * `undefined`. However, it's often best to assert that the target is equal to
    * its expected value.
    *
    *     expect(1).to.equal(1); // Recommended
    *     expect(1).to.exist; // Not recommended
    *
    *     expect(0).to.equal(0); // Recommended
    *     expect(0).to.exist; // Not recommended
    *
    * Add `.not` earlier in the chain to negate `.exist`.
    *
    *     expect(null).to.be.null; // Recommended
    *     expect(null).to.not.exist; // Not recommended
    *
    *     expect(undefined).to.be.undefined; // Recommended
    *     expect(undefined).to.not.exist; // Not recommended
    *
    * A custom error message can be given as the second argument to `expect`.
    *
    *     expect(null, 'nooo why fail??').to.exist;
    *
    * The alias `.exists` can be used interchangeably with `.exist`.
    *
    * @name exist
    * @alias exists
    * @namespace BDD
    * @api public
    */
 
   function assertExist () {
     var val = flag(this, 'object');
     this.assert(
         val !== null && val !== undefined
       , 'expected #{this} to exist'
       , 'expected #{this} to not exist'
     );
   }
 
   Assertion.addProperty('exist', assertExist);
   Assertion.addProperty('exists', assertExist);
 
   /**
    * ### .empty
    *
    * When the target is a string or array, `.empty` asserts that the target's
    * `length` property is strictly (`===`) equal to `0`.
    *
    *     expect([]).to.be.empty;
    *     expect('').to.be.empty;
    *
    * When the target is a map or set, `.empty` asserts that the target's `size`
    * property is strictly equal to `0`.
    *
    *     expect(new Set()).to.be.empty;
    *     expect(new Map()).to.be.empty;
    *
    * When the target is a non-function object, `.empty` asserts that the target
    * doesn't have any own enumerable properties. Properties with Symbol-based
    * keys are excluded from the count.
    *
    *     expect({}).to.be.empty;
    *
    * Because `.empty` does different things based on the target's type, it's
    * important to check the target's type before using `.empty`. See the `.a`
    * doc for info on testing a target's type.
    *
    *     expect([]).to.be.an('array').that.is.empty;
    *
    * Add `.not` earlier in the chain to negate `.empty`. However, it's often
    * best to assert that the target contains its expected number of values,
    * rather than asserting that it's not empty.
    *
    *     expect([1, 2, 3]).to.have.lengthOf(3); // Recommended
    *     expect([1, 2, 3]).to.not.be.empty; // Not recommended
    *
    *     expect(new Set([1, 2, 3])).to.have.property('size', 3); // Recommended
    *     expect(new Set([1, 2, 3])).to.not.be.empty; // Not recommended
    *
    *     expect(Object.keys({a: 1})).to.have.lengthOf(1); // Recommended
    *     expect({a: 1}).to.not.be.empty; // Not recommended
    *
    * A custom error message can be given as the second argument to `expect`.
    *
    *     expect([1, 2, 3], 'nooo why fail??').to.be.empty;
    *
    * @name empty
    * @namespace BDD
    * @api public
    */
 
   Assertion.addProperty('empty', function () {
     var val = flag(this, 'object')
       , ssfi = flag(this, 'ssfi')
       , flagMsg = flag(this, 'message')
       , itemsCount;
 
     flagMsg = flagMsg ? flagMsg + ': ' : '';
 
     switch (_.type(val).toLowerCase()) {
       case 'array':
       case 'string':
         itemsCount = val.length;
         break;
       case 'map':
       case 'set':
         itemsCount = val.size;
         break;
       case 'weakmap':
       case 'weakset':
         throw new AssertionError(
           flagMsg + '.empty was passed a weak collection',
           undefined,
           ssfi
         );
       case 'function':
         var msg = flagMsg + '.empty was passed a function ' + _.getName(val);
         throw new AssertionError(msg.trim(), undefined, ssfi);
       default:
         if (val !== Object(val)) {
           throw new AssertionError(
             flagMsg + '.empty was passed non-string primitive ' + _.inspect(val),
             undefined,
             ssfi
           );
         }
         itemsCount = Object.keys(val).length;
     }
 
     this.assert(
         0 === itemsCount
       , 'expected #{this} to be empty'
       , 'expected #{this} not to be empty'
     );
   });
 
   /**
    * ### .arguments
    *
    * Asserts that the target is an `arguments` object.
    *
    *     function test () {
    *       expect(arguments).to.be.arguments;
    *     }
    *
    *     test();
    *
    * Add `.not` earlier in the chain to negate `.arguments`. However, it's often
    * best to assert which type the target is expected to be, rather than
    * asserting that it’s not an `arguments` object.
    *
    *     expect('foo').to.be.a('string'); // Recommended
    *     expect('foo').to.not.be.arguments; // Not recommended
    *
    * A custom error message can be given as the second argument to `expect`.
    *
    *     expect({}, 'nooo why fail??').to.be.arguments;
    *
    * The alias `.Arguments` can be used interchangeably with `.arguments`.
    *
    * @name arguments
    * @alias Arguments
    * @namespace BDD
    * @api public
    */
 
   function checkArguments () {
     var obj = flag(this, 'object')
       , type = _.type(obj);
     this.assert(
         'Arguments' === type
       , 'expected #{this} to be arguments but got ' + type
       , 'expected #{this} to not be arguments'
     );
   }
 
   Assertion.addProperty('arguments', checkArguments);
   Assertion.addProperty('Arguments', checkArguments);
 
   /**
    * ### .equal(val[, msg])
    *
    * Asserts that the target is strictly (`===`) equal to the given `val`.
    *
    *     expect(1).to.equal(1);
    *     expect('foo').to.equal('foo');
    *
    * Add `.deep` earlier in the chain to use deep equality instead. See the
    * `deep-eql` project page for info on the deep equality algorithm:
    * https://github.com/chaijs/deep-eql.
    *
    *     // Target object deeply (but not strictly) equals `{a: 1}`
    *     expect({a: 1}).to.deep.equal({a: 1});
    *     expect({a: 1}).to.not.equal({a: 1});
    *
    *     // Target array deeply (but not strictly) equals `[1, 2]`
    *     expect([1, 2]).to.deep.equal([1, 2]);
    *     expect([1, 2]).to.not.equal([1, 2]);
    *
    * Add `.not` earlier in the chain to negate `.equal`. However, it's often
    * best to assert that the target is equal to its expected value, rather than
    * not equal to one of countless unexpected values.
    *
    *     expect(1).to.equal(1); // Recommended
    *     expect(1).to.not.equal(2); // Not recommended
    *
    * `.equal` accepts an optional `msg` argument which is a custom error message
    * to show when the assertion fails. The message can also be given as the
    * second argument to `expect`.
    *
    *     expect(1).to.equal(2, 'nooo why fail??');
    *     expect(1, 'nooo why fail??').to.equal(2);
    *
    * The aliases `.equals` and `eq` can be used interchangeably with `.equal`.
    *
    * @name equal
    * @alias equals
    * @alias eq
    * @param {Mixed} val
    * @param {String} msg _optional_
    * @namespace BDD
    * @api public
    */
 
   function assertEqual (val, msg) {
     if (msg) flag(this, 'message', msg);
     var obj = flag(this, 'object');
     if (flag(this, 'deep')) {
       var prevLockSsfi = flag(this, 'lockSsfi');
       flag(this, 'lockSsfi', true);
       this.eql(val);
       flag(this, 'lockSsfi', prevLockSsfi);
     } else {
       this.assert(
           val === obj
         , 'expected #{this} to equal #{exp}'
         , 'expected #{this} to not equal #{exp}'
         , val
         , this._obj
         , true
       );
     }
   }
 
   Assertion.addMethod('equal', assertEqual);
   Assertion.addMethod('equals', assertEqual);
   Assertion.addMethod('eq', assertEqual);
 
   /**
    * ### .eql(obj[, msg])
    *
    * Asserts that the target is deeply equal to the given `obj`. See the
    * `deep-eql` project page for info on the deep equality algorithm:
    * https://github.com/chaijs/deep-eql.
    *
    *     // Target object is deeply (but not strictly) equal to {a: 1}
    *     expect({a: 1}).to.eql({a: 1}).but.not.equal({a: 1});
    *
    *     // Target array is deeply (but not strictly) equal to [1, 2]
    *     expect([1, 2]).to.eql([1, 2]).but.not.equal([1, 2]);
    *
    * Add `.not` earlier in the chain to negate `.eql`. However, it's often best
    * to assert that the target is deeply equal to its expected value, rather
    * than not deeply equal to one of countless unexpected values.
    *
    *     expect({a: 1}).to.eql({a: 1}); // Recommended
    *     expect({a: 1}).to.not.eql({b: 2}); // Not recommended
    *
    * `.eql` accepts an optional `msg` argument which is a custom error message
    * to show when the assertion fails. The message can also be given as the
    * second argument to `expect`.
    *
    *     expect({a: 1}).to.eql({b: 2}, 'nooo why fail??');
    *     expect({a: 1}, 'nooo why fail??').to.eql({b: 2});
    *
    * The alias `.eqls` can be used interchangeably with `.eql`.
    *
    * The `.deep.equal` assertion is almost identical to `.eql` but with one
    * difference: `.deep.equal` causes deep equality comparisons to also be used
    * for any other assertions that follow in the chain.
    *
    * @name eql
    * @alias eqls
    * @param {Mixed} obj
    * @param {String} msg _optional_
    * @namespace BDD
    * @api public
    */
 
   function assertEql(obj, msg) {
     if (msg) flag(this, 'message', msg);
     this.assert(
         _.eql(obj, flag(this, 'object'))
       , 'expected #{this} to deeply equal #{exp}'
       , 'expected #{this} to not deeply equal #{exp}'
       , obj
       , this._obj
       , true
     );
   }
 
   Assertion.addMethod('eql', assertEql);
   Assertion.addMethod('eqls', assertEql);
 
   /**
    * ### .above(n[, msg])
    *
    * Asserts that the target is a number or a date greater than the given number or date `n` respectively.
    * However, it's often best to assert that the target is equal to its expected
    * value.
    *
    *     expect(2).to.equal(2); // Recommended
    *     expect(2).to.be.above(1); // Not recommended
    *
    * Add `.lengthOf` earlier in the chain to assert that the target's `length`
    * or `size` is greater than the given number `n`.
    *
    *     expect('foo').to.have.lengthOf(3); // Recommended
    *     expect('foo').to.have.lengthOf.above(2); // Not recommended
    *
    *     expect([1, 2, 3]).to.have.lengthOf(3); // Recommended
    *     expect([1, 2, 3]).to.have.lengthOf.above(2); // Not recommended
    *
    * Add `.not` earlier in the chain to negate `.above`.
    *
    *     expect(2).to.equal(2); // Recommended
    *     expect(1).to.not.be.above(2); // Not recommended
    *
    * `.above` accepts an optional `msg` argument which is a custom error message
    * to show when the assertion fails. The message can also be given as the
    * second argument to `expect`.
    *
    *     expect(1).to.be.above(2, 'nooo why fail??');
    *     expect(1, 'nooo why fail??').to.be.above(2);
    *
    * The aliases `.gt` and `.greaterThan` can be used interchangeably with
    * `.above`.
    *
    * @name above
    * @alias gt
    * @alias greaterThan
    * @param {Number} n
    * @param {String} msg _optional_
    * @namespace BDD
    * @api public
    */
 
   function assertAbove (n, msg) {
     if (msg) flag(this, 'message', msg);
     var obj = flag(this, 'object')
       , doLength = flag(this, 'doLength')
       , flagMsg = flag(this, 'message')
       , msgPrefix = ((flagMsg) ? flagMsg + ': ' : '')
       , ssfi = flag(this, 'ssfi')
       , objType = _.type(obj).toLowerCase()
       , nType = _.type(n).toLowerCase()
       , errorMessage
       , shouldThrow = true;
 
     if (doLength && objType !== 'map' && objType !== 'set') {
       new Assertion(obj, flagMsg, ssfi, true).to.have.property('length');
     }
 
     if (!doLength && (objType === 'date' && nType !== 'date')) {
       errorMessage = msgPrefix + 'the argument to above must be a date';
     } else if (nType !== 'number' && (doLength || objType === 'number')) {
       errorMessage = msgPrefix + 'the argument to above must be a number';
     } else if (!doLength && (objType !== 'date' && objType !== 'number')) {
       var printObj = (objType === 'string') ? "'" + obj + "'" : obj;
       errorMessage = msgPrefix + 'expected ' + printObj + ' to be a number or a date';
     } else {
       shouldThrow = false;
     }
 
     if (shouldThrow) {
       throw new AssertionError(errorMessage, undefined, ssfi);
     }
 
     if (doLength) {
       var descriptor = 'length'
         , itemsCount;
       if (objType === 'map' || objType === 'set') {
         descriptor = 'size';
         itemsCount = obj.size;
       } else {
         itemsCount = obj.length;
       }
       this.assert(
           itemsCount > n
         , 'expected #{this} to have a ' + descriptor + ' above #{exp} but got #{act}'
         , 'expected #{this} to not have a ' + descriptor + ' above #{exp}'
         , n
         , itemsCount
       );
     } else {
       this.assert(
           obj > n
         , 'expected #{this} to be above #{exp}'
         , 'expected #{this} to be at most #{exp}'
         , n
       );
     }
   }
 
   Assertion.addMethod('above', assertAbove);
   Assertion.addMethod('gt', assertAbove);
   Assertion.addMethod('greaterThan', assertAbove);
 
   /**
    * ### .least(n[, msg])
    *
    * Asserts that the target is a number or a date greater than or equal to the given
    * number or date `n` respectively. However, it's often best to assert that the target is equal to
    * its expected value.
    *
    *     expect(2).to.equal(2); // Recommended
    *     expect(2).to.be.at.least(1); // Not recommended
    *     expect(2).to.be.at.least(2); // Not recommended
    *
    * Add `.lengthOf` earlier in the chain to assert that the target's `length`
    * or `size` is greater than or equal to the given number `n`.
    *
    *     expect('foo').to.have.lengthOf(3); // Recommended
    *     expect('foo').to.have.lengthOf.at.least(2); // Not recommended
    *
    *     expect([1, 2, 3]).to.have.lengthOf(3); // Recommended
    *     expect([1, 2, 3]).to.have.lengthOf.at.least(2); // Not recommended
    *
    * Add `.not` earlier in the chain to negate `.least`.
    *
    *     expect(1).to.equal(1); // Recommended
    *     expect(1).to.not.be.at.least(2); // Not recommended
    *
    * `.least` accepts an optional `msg` argument which is a custom error message
    * to show when the assertion fails. The message can also be given as the
    * second argument to `expect`.
    *
    *     expect(1).to.be.at.least(2, 'nooo why fail??');
    *     expect(1, 'nooo why fail??').to.be.at.least(2);
    *
    * The aliases `.gte` and `.greaterThanOrEqual` can be used interchangeably with
    * `.least`.
    *
    * @name least
    * @alias gte
    * @alias greaterThanOrEqual
    * @param {Number} n
    * @param {String} msg _optional_
    * @namespace BDD
    * @api public
    */
 
   function assertLeast (n, msg) {
     if (msg) flag(this, 'message', msg);
     var obj = flag(this, 'object')
       , doLength = flag(this, 'doLength')
       , flagMsg = flag(this, 'message')
       , msgPrefix = ((flagMsg) ? flagMsg + ': ' : '')
       , ssfi = flag(this, 'ssfi')
       , objType = _.type(obj).toLowerCase()
       , nType = _.type(n).toLowerCase()
       , errorMessage
       , shouldThrow = true;
 
     if (doLength && objType !== 'map' && objType !== 'set') {
       new Assertion(obj, flagMsg, ssfi, true).to.have.property('length');
     }
 
     if (!doLength && (objType === 'date' && nType !== 'date')) {
       errorMessage = msgPrefix + 'the argument to least must be a date';
     } else if (nType !== 'number' && (doLength || objType === 'number')) {
       errorMessage = msgPrefix + 'the argument to least must be a number';
     } else if (!doLength && (objType !== 'date' && objType !== 'number')) {
       var printObj = (objType === 'string') ? "'" + obj + "'" : obj;
       errorMessage = msgPrefix + 'expected ' + printObj + ' to be a number or a date';
     } else {
       shouldThrow = false;
     }
 
     if (shouldThrow) {
       throw new AssertionError(errorMessage, undefined, ssfi);
     }
 
     if (doLength) {
       var descriptor = 'length'
         , itemsCount;
       if (objType === 'map' || objType === 'set') {
         descriptor = 'size';
         itemsCount = obj.size;
       } else {
         itemsCount = obj.length;
       }
       this.assert(
           itemsCount >= n
         , 'expected #{this} to have a ' + descriptor + ' at least #{exp} but got #{act}'
         , 'expected #{this} to have a ' + descriptor + ' below #{exp}'
         , n
         , itemsCount
       );
     } else {
       this.assert(
           obj >= n
         , 'expected #{this} to be at least #{exp}'
         , 'expected #{this} to be below #{exp}'
         , n
       );
     }
   }
 
   Assertion.addMethod('least', assertLeast);
   Assertion.addMethod('gte', assertLeast);
   Assertion.addMethod('greaterThanOrEqual', assertLeast);
 
   /**
    * ### .below(n[, msg])
    *
    * Asserts that the target is a number or a date less than the given number or date `n` respectively.
    * However, it's often best to assert that the target is equal to its expected
    * value.
    *
    *     expect(1).to.equal(1); // Recommended
    *     expect(1).to.be.below(2); // Not recommended
    *
    * Add `.lengthOf` earlier in the chain to assert that the target's `length`
    * or `size` is less than the given number `n`.
    *
    *     expect('foo').to.have.lengthOf(3); // Recommended
    *     expect('foo').to.have.lengthOf.below(4); // Not recommended
    *
    *     expect([1, 2, 3]).to.have.length(3); // Recommended
    *     expect([1, 2, 3]).to.have.lengthOf.below(4); // Not recommended
    *
    * Add `.not` earlier in the chain to negate `.below`.
    *
    *     expect(2).to.equal(2); // Recommended
    *     expect(2).to.not.be.below(1); // Not recommended
    *
    * `.below` accepts an optional `msg` argument which is a custom error message
    * to show when the assertion fails. The message can also be given as the
    * second argument to `expect`.
    *
    *     expect(2).to.be.below(1, 'nooo why fail??');
    *     expect(2, 'nooo why fail??').to.be.below(1);
    *
    * The aliases `.lt` and `.lessThan` can be used interchangeably with
    * `.below`.
    *
    * @name below
    * @alias lt
    * @alias lessThan
    * @param {Number} n
    * @param {String} msg _optional_
    * @namespace BDD
    * @api public
    */
 
   function assertBelow (n, msg) {
     if (msg) flag(this, 'message', msg);
     var obj = flag(this, 'object')
       , doLength = flag(this, 'doLength')
       , flagMsg = flag(this, 'message')
       , msgPrefix = ((flagMsg) ? flagMsg + ': ' : '')
       , ssfi = flag(this, 'ssfi')
       , objType = _.type(obj).toLowerCase()
       , nType = _.type(n).toLowerCase()
       , errorMessage
       , shouldThrow = true;
 
     if (doLength && objType !== 'map' && objType !== 'set') {
       new Assertion(obj, flagMsg, ssfi, true).to.have.property('length');
     }
 
     if (!doLength && (objType === 'date' && nType !== 'date')) {
       errorMessage = msgPrefix + 'the argument to below must be a date';
     } else if (nType !== 'number' && (doLength || objType === 'number')) {
       errorMessage = msgPrefix + 'the argument to below must be a number';
     } else if (!doLength && (objType !== 'date' && objType !== 'number')) {
       var printObj = (objType === 'string') ? "'" + obj + "'" : obj;
       errorMessage = msgPrefix + 'expected ' + printObj + ' to be a number or a date';
     } else {
       shouldThrow = false;
     }
 
     if (shouldThrow) {
       throw new AssertionError(errorMessage, undefined, ssfi);
     }
 
     if (doLength) {
       var descriptor = 'length'
         , itemsCount;
       if (objType === 'map' || objType === 'set') {
         descriptor = 'size';
         itemsCount = obj.size;
       } else {
         itemsCount = obj.length;
       }
       this.assert(
           itemsCount < n
         , 'expected #{this} to have a ' + descriptor + ' below #{exp} but got #{act}'
         , 'expected #{this} to not have a ' + descriptor + ' below #{exp}'
         , n
         , itemsCount
       );
     } else {
       this.assert(
           obj < n
         , 'expected #{this} to be below #{exp}'
         , 'expected #{this} to be at least #{exp}'
         , n
       );
     }
   }
 
   Assertion.addMethod('below', assertBelow);
   Assertion.addMethod('lt', assertBelow);
   Assertion.addMethod('lessThan', assertBelow);
 
   /**
    * ### .most(n[, msg])
    *
    * Asserts that the target is a number or a date less than or equal to the given number
    * or date `n` respectively. However, it's often best to assert that the target is equal to its
    * expected value.
    *
    *     expect(1).to.equal(1); // Recommended
    *     expect(1).to.be.at.most(2); // Not recommended
    *     expect(1).to.be.at.most(1); // Not recommended
    *
    * Add `.lengthOf` earlier in the chain to assert that the target's `length`
    * or `size` is less than or equal to the given number `n`.
    *
    *     expect('foo').to.have.lengthOf(3); // Recommended
    *     expect('foo').to.have.lengthOf.at.most(4); // Not recommended
    *
    *     expect([1, 2, 3]).to.have.lengthOf(3); // Recommended
    *     expect([1, 2, 3]).to.have.lengthOf.at.most(4); // Not recommended
    *
    * Add `.not` earlier in the chain to negate `.most`.
    *
    *     expect(2).to.equal(2); // Recommended
    *     expect(2).to.not.be.at.most(1); // Not recommended
    *
    * `.most` accepts an optional `msg` argument which is a custom error message
    * to show when the assertion fails. The message can also be given as the
    * second argument to `expect`.
    *
    *     expect(2).to.be.at.most(1, 'nooo why fail??');
    *     expect(2, 'nooo why fail??').to.be.at.most(1);
    *
    * The aliases `.lte` and `.lessThanOrEqual` can be used interchangeably with
    * `.most`.
    *
    * @name most
    * @alias lte
    * @alias lessThanOrEqual
    * @param {Number} n
    * @param {String} msg _optional_
    * @namespace BDD
    * @api public
    */
 
   function assertMost (n, msg) {
     if (msg) flag(this, 'message', msg);
     var obj = flag(this, 'object')
       , doLength = flag(this, 'doLength')
       , flagMsg = flag(this, 'message')
       , msgPrefix = ((flagMsg) ? flagMsg + ': ' : '')
       , ssfi = flag(this, 'ssfi')
       , objType = _.type(obj).toLowerCase()
       , nType = _.type(n).toLowerCase()
       , errorMessage
       , shouldThrow = true;
 
     if (doLength && objType !== 'map' && objType !== 'set') {
       new Assertion(obj, flagMsg, ssfi, true).to.have.property('length');
     }
 
     if (!doLength && (objType === 'date' && nType !== 'date')) {
       errorMessage = msgPrefix + 'the argument to most must be a date';
     } else if (nType !== 'number' && (doLength || objType === 'number')) {
       errorMessage = msgPrefix + 'the argument to most must be a number';
     } else if (!doLength && (objType !== 'date' && objType !== 'number')) {
       var printObj = (objType === 'string') ? "'" + obj + "'" : obj;
       errorMessage = msgPrefix + 'expected ' + printObj + ' to be a number or a date';
     } else {
       shouldThrow = false;
     }
 
     if (shouldThrow) {
       throw new AssertionError(errorMessage, undefined, ssfi);
     }
 
     if (doLength) {
       var descriptor = 'length'
         , itemsCount;
       if (objType === 'map' || objType === 'set') {
         descriptor = 'size';
         itemsCount = obj.size;
       } else {
         itemsCount = obj.length;
       }
       this.assert(
           itemsCount <= n
         , 'expected #{this} to have a ' + descriptor + ' at most #{exp} but got #{act}'
         , 'expected #{this} to have a ' + descriptor + ' above #{exp}'
         , n
         , itemsCount
       );
     } else {
       this.assert(
           obj <= n
         , 'expected #{this} to be at most #{exp}'
         , 'expected #{this} to be above #{exp}'
         , n
       );
     }
   }
 
   Assertion.addMethod('most', assertMost);
   Assertion.addMethod('lte', assertMost);
   Assertion.addMethod('lessThanOrEqual', assertMost);
 
   /**
    * ### .within(start, finish[, msg])
    *
    * Asserts that the target is a number or a date greater than or equal to the given
    * number or date `start`, and less than or equal to the given number or date `finish` respectively.
    * However, it's often best to assert that the target is equal to its expected
    * value.
    *
    *     expect(2).to.equal(2); // Recommended
    *     expect(2).to.be.within(1, 3); // Not recommended
    *     expect(2).to.be.within(2, 3); // Not recommended
    *     expect(2).to.be.within(1, 2); // Not recommended
    *
    * Add `.lengthOf` earlier in the chain to assert that the target's `length`
    * or `size` is greater than or equal to the given number `start`, and less
    * than or equal to the given number `finish`.
    *
    *     expect('foo').to.have.lengthOf(3); // Recommended
    *     expect('foo').to.have.lengthOf.within(2, 4); // Not recommended
    *
    *     expect([1, 2, 3]).to.have.lengthOf(3); // Recommended
    *     expect([1, 2, 3]).to.have.lengthOf.within(2, 4); // Not recommended
    *
    * Add `.not` earlier in the chain to negate `.within`.
    *
    *     expect(1).to.equal(1); // Recommended
    *     expect(1).to.not.be.within(2, 4); // Not recommended
    *
    * `.within` accepts an optional `msg` argument which is a custom error
    * message to show when the assertion fails. The message can also be given as
    * the second argument to `expect`.
    *
    *     expect(4).to.be.within(1, 3, 'nooo why fail??');
    *     expect(4, 'nooo why fail??').to.be.within(1, 3);
    *
    * @name within
    * @param {Number} start lower bound inclusive
    * @param {Number} finish upper bound inclusive
    * @param {String} msg _optional_
    * @namespace BDD
    * @api public
    */
 
   Assertion.addMethod('within', function (start, finish, msg) {
     if (msg) flag(this, 'message', msg);
     var obj = flag(this, 'object')
       , doLength = flag(this, 'doLength')
       , flagMsg = flag(this, 'message')
       , msgPrefix = ((flagMsg) ? flagMsg + ': ' : '')
       , ssfi = flag(this, 'ssfi')
       , objType = _.type(obj).toLowerCase()
       , startType = _.type(start).toLowerCase()
       , finishType = _.type(finish).toLowerCase()
       , errorMessage
       , shouldThrow = true
       , range = (startType === 'date' && finishType === 'date')
           ? start.toUTCString() + '..' + finish.toUTCString()
           : start + '..' + finish;
 
     if (doLength && objType !== 'map' && objType !== 'set') {
       new Assertion(obj, flagMsg, ssfi, true).to.have.property('length');
     }
 
     if (!doLength && (objType === 'date' && (startType !== 'date' || finishType !== 'date'))) {
       errorMessage = msgPrefix + 'the arguments to within must be dates';
     } else if ((startType !== 'number' || finishType !== 'number') && (doLength || objType === 'number')) {
       errorMessage = msgPrefix + 'the arguments to within must be numbers';
     } else if (!doLength && (objType !== 'date' && objType !== 'number')) {
       var printObj = (objType === 'string') ? "'" + obj + "'" : obj;
       errorMessage = msgPrefix + 'expected ' + printObj + ' to be a number or a date';
     } else {
       shouldThrow = false;
     }
 
     if (shouldThrow) {
       throw new AssertionError(errorMessage, undefined, ssfi);
     }
 
     if (doLength) {
       var descriptor = 'length'
         , itemsCount;
       if (objType === 'map' || objType === 'set') {
         descriptor = 'size';
         itemsCount = obj.size;
       } else {
         itemsCount = obj.length;
       }
       this.assert(
           itemsCount >= start && itemsCount <= finish
         , 'expected #{this} to have a ' + descriptor + ' within ' + range
         , 'expected #{this} to not have a ' + descriptor + ' within ' + range
       );
     } else {
       this.assert(
           obj >= start && obj <= finish
         , 'expected #{this} to be within ' + range
         , 'expected #{this} to not be within ' + range
       );
     }
   });
 
   /**
    * ### .instanceof(constructor[, msg])
    *
    * Asserts that the target is an instance of the given `constructor`.
    *
    *     function Cat () { }
    *
    *     expect(new Cat()).to.be.an.instanceof(Cat);
    *     expect([1, 2]).to.be.an.instanceof(Array);
    *
    * Add `.not` earlier in the chain to negate `.instanceof`.
    *
    *     expect({a: 1}).to.not.be.an.instanceof(Array);
    *
    * `.instanceof` accepts an optional `msg` argument which is a custom error
    * message to show when the assertion fails. The message can also be given as
    * the second argument to `expect`.
    *
    *     expect(1).to.be.an.instanceof(Array, 'nooo why fail??');
    *     expect(1, 'nooo why fail??').to.be.an.instanceof(Array);
    *
    * Due to limitations in ES5, `.instanceof` may not always work as expected
    * when using a transpiler such as Babel or TypeScript. In particular, it may
    * produce unexpected results when subclassing built-in object such as
    * `Array`, `Error`, and `Map`. See your transpiler's docs for details:
    *
    * - ([Babel](https://babeljs.io/docs/usage/caveats/#classes))
    * - ([TypeScript](https://github.com/Microsoft/TypeScript/wiki/Breaking-Changes#extending-built-ins-like-error-array-and-map-may-no-longer-work))
    *
    * The alias `.instanceOf` can be used interchangeably with `.instanceof`.
    *
    * @name instanceof
    * @param {Constructor} constructor
    * @param {String} msg _optional_
    * @alias instanceOf
    * @namespace BDD
    * @api public
    */
 
   function assertInstanceOf (constructor, msg) {
     if (msg) flag(this, 'message', msg);
 
     var target = flag(this, 'object')
     var ssfi = flag(this, 'ssfi');
     var flagMsg = flag(this, 'message');
 
     try {
       var isInstanceOf = target instanceof constructor;
     } catch (err) {
       if (err instanceof TypeError) {
         flagMsg = flagMsg ? flagMsg + ': ' : '';
         throw new AssertionError(
           flagMsg + 'The instanceof assertion needs a constructor but '
             + _.type(constructor) + ' was given.',
           undefined,
           ssfi
         );
       }
       throw err;
     }
 
     var name = _.getName(constructor);
     if (name === null) {
       name = 'an unnamed constructor';
     }
 
     this.assert(
         isInstanceOf
       , 'expected #{this} to be an instance of ' + name
       , 'expected #{this} to not be an instance of ' + name
     );
   };
 
   Assertion.addMethod('instanceof', assertInstanceOf);
   Assertion.addMethod('instanceOf', assertInstanceOf);
 
   /**
    * ### .property(name[, val[, msg]])
    *
    * Asserts that the target has a property with the given key `name`.
    *
    *     expect({a: 1}).to.have.property('a');
    *
    * When `val` is provided, `.property` also asserts that the property's value
    * is equal to the given `val`.
    *
    *     expect({a: 1}).to.have.property('a', 1);
    *
    * By default, strict (`===`) equality is used. Add `.deep` earlier in the
    * chain to use deep equality instead. See the `deep-eql` project page for
    * info on the deep equality algorithm: https://github.com/chaijs/deep-eql.
    *
    *     // Target object deeply (but not strictly) has property `x: {a: 1}`
    *     expect({x: {a: 1}}).to.have.deep.property('x', {a: 1});
    *     expect({x: {a: 1}}).to.not.have.property('x', {a: 1});
    *
    * The target's enumerable and non-enumerable properties are always included
    * in the search. By default, both own and inherited properties are included.
    * Add `.own` earlier in the chain to exclude inherited properties from the
    * search.
    *
    *     Object.prototype.b = 2;
    *
    *     expect({a: 1}).to.have.own.property('a');
    *     expect({a: 1}).to.have.own.property('a', 1);
    *     expect({a: 1}).to.have.property('b');
    *     expect({a: 1}).to.not.have.own.property('b');
    *
    * `.deep` and `.own` can be combined.
    *
    *     expect({x: {a: 1}}).to.have.deep.own.property('x', {a: 1});
    *
    * Add `.nested` earlier in the chain to enable dot- and bracket-notation when
    * referencing nested properties.
    *
    *     expect({a: {b: ['x', 'y']}}).to.have.nested.property('a.b[1]');
    *     expect({a: {b: ['x', 'y']}}).to.have.nested.property('a.b[1]', 'y');
    *
    * If `.` or `[]` are part of an actual property name, they can be escaped by
    * adding two backslashes before them.
    *
    *     expect({'.a': {'[b]': 'x'}}).to.have.nested.property('\\.a.\\[b\\]');
    *
    * `.deep` and `.nested` can be combined.
    *
    *     expect({a: {b: [{c: 3}]}})
    *       .to.have.deep.nested.property('a.b[0]', {c: 3});
    *
    * `.own` and `.nested` cannot be combined.
    *
    * Add `.not` earlier in the chain to negate `.property`.
    *
    *     expect({a: 1}).to.not.have.property('b');
    *
    * However, it's dangerous to negate `.property` when providing `val`. The
    * problem is that it creates uncertain expectations by asserting that the
    * target either doesn't have a property with the given key `name`, or that it
    * does have a property with the given key `name` but its value isn't equal to
    * the given `val`. It's often best to identify the exact output that's
    * expected, and then write an assertion that only accepts that exact output.
    *
    * When the target isn't expected to have a property with the given key
    * `name`, it's often best to assert exactly that.
    *
    *     expect({b: 2}).to.not.have.property('a'); // Recommended
    *     expect({b: 2}).to.not.have.property('a', 1); // Not recommended
    *
    * When the target is expected to have a property with the given key `name`,
    * it's often best to assert that the property has its expected value, rather
    * than asserting that it doesn't have one of many unexpected values.
    *
    *     expect({a: 3}).to.have.property('a', 3); // Recommended
    *     expect({a: 3}).to.not.have.property('a', 1); // Not recommended
    *
    * `.property` changes the target of any assertions that follow in the chain
    * to be the value of the property from the original target object.
    *
    *     expect({a: 1}).to.have.property('a').that.is.a('number');
    *
    * `.property` accepts an optional `msg` argument which is a custom error
    * message to show when the assertion fails. The message can also be given as
    * the second argument to `expect`. When not providing `val`, only use the
    * second form.
    *
    *     // Recommended
    *     expect({a: 1}).to.have.property('a', 2, 'nooo why fail??');
    *     expect({a: 1}, 'nooo why fail??').to.have.property('a', 2);
    *     expect({a: 1}, 'nooo why fail??').to.have.property('b');
    *
    *     // Not recommended
    *     expect({a: 1}).to.have.property('b', undefined, 'nooo why fail??');
    *
    * The above assertion isn't the same thing as not providing `val`. Instead,
    * it's asserting that the target object has a `b` property that's equal to
    * `undefined`.
    *
    * The assertions `.ownProperty` and `.haveOwnProperty` can be used
    * interchangeably with `.own.property`.
    *
    * @name property
    * @param {String} name
    * @param {Mixed} val (optional)
    * @param {String} msg _optional_
    * @returns value of property for chaining
    * @namespace BDD
    * @api public
    */
 
   function assertProperty (name, val, msg) {
     if (msg) flag(this, 'message', msg);
 
     var isNested = flag(this, 'nested')
       , isOwn = flag(this, 'own')
       , flagMsg = flag(this, 'message')
       , obj = flag(this, 'object')
       , ssfi = flag(this, 'ssfi')
       , nameType = typeof name;
 
     flagMsg = flagMsg ? flagMsg + ': ' : '';
 
     if (isNested) {
       if (nameType !== 'string') {
         throw new AssertionError(
           flagMsg + 'the argument to property must be a string when using nested syntax',
           undefined,
           ssfi
         );
       }
     } else {
       if (nameType !== 'string' && nameType !== 'number' && nameType !== 'symbol') {
         throw new AssertionError(
           flagMsg + 'the argument to property must be a string, number, or symbol',
           undefined,
           ssfi
         );
       }
     }
 
     if (isNested && isOwn) {
       throw new AssertionError(
         flagMsg + 'The "nested" and "own" flags cannot be combined.',
         undefined,
         ssfi
       );
     }
 
     if (obj === null || obj === undefined) {
       throw new AssertionError(
         flagMsg + 'Target cannot be null or undefined.',
         undefined,
         ssfi
       );
     }
 
     var isDeep = flag(this, 'deep')
       , negate = flag(this, 'negate')
       , pathInfo = isNested ? _.getPathInfo(obj, name) : null
       , value = isNested ? pathInfo.value : obj[name];
 
     var descriptor = '';
     if (isDeep) descriptor += 'deep ';
     if (isOwn) descriptor += 'own ';
     if (isNested) descriptor += 'nested ';
     descriptor += 'property ';
 
     var hasProperty;
     if (isOwn) hasProperty = Object.prototype.hasOwnProperty.call(obj, name);
     else if (isNested) hasProperty = pathInfo.exists;
     else hasProperty = _.hasProperty(obj, name);
 
     // When performing a negated assertion for both name and val, merely having
     // a property with the given name isn't enough to cause the assertion to
     // fail. It must both have a property with the given name, and the value of
     // that property must equal the given val. Therefore, skip this assertion in
     // favor of the next.
     if (!negate || arguments.length === 1) {
       this.assert(
           hasProperty
         , 'expected #{this} to have ' + descriptor + _.inspect(name)
         , 'expected #{this} to not have ' + descriptor + _.inspect(name));
     }
 
     if (arguments.length > 1) {
       this.assert(
           hasProperty && (isDeep ? _.eql(val, value) : val === value)
         , 'expected #{this} to have ' + descriptor + _.inspect(name) + ' of #{exp}, but got #{act}'
         , 'expected #{this} to not have ' + descriptor + _.inspect(name) + ' of #{act}'
         , val
         , value
       );
     }
 
     flag(this, 'object', value);
   }
 
   Assertion.addMethod('property', assertProperty);
 
   function assertOwnProperty (name, value, msg) {
     flag(this, 'own', true);
     assertProperty.apply(this, arguments);
   }
 
   Assertion.addMethod('ownProperty', assertOwnProperty);
   Assertion.addMethod('haveOwnProperty', assertOwnProperty);
 
   /**
    * ### .ownPropertyDescriptor(name[, descriptor[, msg]])
    *
    * Asserts that the target has its own property descriptor with the given key
    * `name`. Enumerable and non-enumerable properties are included in the
    * search.
    *
    *     expect({a: 1}).to.have.ownPropertyDescriptor('a');
    *
    * When `descriptor` is provided, `.ownPropertyDescriptor` also asserts that
    * the property's descriptor is deeply equal to the given `descriptor`. See
    * the `deep-eql` project page for info on the deep equality algorithm:
    * https://github.com/chaijs/deep-eql.
    *
    *     expect({a: 1}).to.have.ownPropertyDescriptor('a', {
    *       configurable: true,
    *       enumerable: true,
    *       writable: true,
    *       value: 1,
    *     });
    *
    * Add `.not` earlier in the chain to negate `.ownPropertyDescriptor`.
    *
    *     expect({a: 1}).to.not.have.ownPropertyDescriptor('b');
    *
    * However, it's dangerous to negate `.ownPropertyDescriptor` when providing
    * a `descriptor`. The problem is that it creates uncertain expectations by
    * asserting that the target either doesn't have a property descriptor with
    * the given key `name`, or that it does have a property descriptor with the
    * given key `name` but it’s not deeply equal to the given `descriptor`. It's
    * often best to identify the exact output that's expected, and then write an
    * assertion that only accepts that exact output.
    *
    * When the target isn't expected to have a property descriptor with the given
    * key `name`, it's often best to assert exactly that.
    *
    *     // Recommended
    *     expect({b: 2}).to.not.have.ownPropertyDescriptor('a');
    *
    *     // Not recommended
    *     expect({b: 2}).to.not.have.ownPropertyDescriptor('a', {
    *       configurable: true,
    *       enumerable: true,
    *       writable: true,
    *       value: 1,
    *     });
    *
    * When the target is expected to have a property descriptor with the given
    * key `name`, it's often best to assert that the property has its expected
    * descriptor, rather than asserting that it doesn't have one of many
    * unexpected descriptors.
    *
    *     // Recommended
    *     expect({a: 3}).to.have.ownPropertyDescriptor('a', {
    *       configurable: true,
    *       enumerable: true,
    *       writable: true,
    *       value: 3,
    *     });
    *
    *     // Not recommended
    *     expect({a: 3}).to.not.have.ownPropertyDescriptor('a', {
    *       configurable: true,
    *       enumerable: true,
    *       writable: true,
    *       value: 1,
    *     });
    *
    * `.ownPropertyDescriptor` changes the target of any assertions that follow
    * in the chain to be the value of the property descriptor from the original
    * target object.
    *
    *     expect({a: 1}).to.have.ownPropertyDescriptor('a')
    *       .that.has.property('enumerable', true);
    *
    * `.ownPropertyDescriptor` accepts an optional `msg` argument which is a
    * custom error message to show when the assertion fails. The message can also
    * be given as the second argument to `expect`. When not providing
    * `descriptor`, only use the second form.
    *
    *     // Recommended
    *     expect({a: 1}).to.have.ownPropertyDescriptor('a', {
    *       configurable: true,
    *       enumerable: true,
    *       writable: true,
    *       value: 2,
    *     }, 'nooo why fail??');
    *
    *     // Recommended
    *     expect({a: 1}, 'nooo why fail??').to.have.ownPropertyDescriptor('a', {
    *       configurable: true,
    *       enumerable: true,
    *       writable: true,
    *       value: 2,
    *     });
    *
    *     // Recommended
    *     expect({a: 1}, 'nooo why fail??').to.have.ownPropertyDescriptor('b');
    *
    *     // Not recommended
    *     expect({a: 1})
    *       .to.have.ownPropertyDescriptor('b', undefined, 'nooo why fail??');
    *
    * The above assertion isn't the same thing as not providing `descriptor`.
    * Instead, it's asserting that the target object has a `b` property
    * descriptor that's deeply equal to `undefined`.
    *
    * The alias `.haveOwnPropertyDescriptor` can be used interchangeably with
    * `.ownPropertyDescriptor`.
    *
    * @name ownPropertyDescriptor
    * @alias haveOwnPropertyDescriptor
    * @param {String} name
    * @param {Object} descriptor _optional_
    * @param {String} msg _optional_
    * @namespace BDD
    * @api public
    */
 
   function assertOwnPropertyDescriptor (name, descriptor, msg) {
     if (typeof descriptor === 'string') {
       msg = descriptor;
       descriptor = null;
     }
     if (msg) flag(this, 'message', msg);
     var obj = flag(this, 'object');
     var actualDescriptor = Object.getOwnPropertyDescriptor(Object(obj), name);
     if (actualDescriptor && descriptor) {
       this.assert(
           _.eql(descriptor, actualDescriptor)
         , 'expected the own property descriptor for ' + _.inspect(name) + ' on #{this} to match ' + _.inspect(descriptor) + ', got ' + _.inspect(actualDescriptor)
         , 'expected the own property descriptor for ' + _.inspect(name) + ' on #{this} to not match ' + _.inspect(descriptor)
         , descriptor
         , actualDescriptor
         , true
       );
     } else {
       this.assert(
           actualDescriptor
         , 'expected #{this} to have an own property descriptor for ' + _.inspect(name)
         , 'expected #{this} to not have an own property descriptor for ' + _.inspect(name)
       );
     }
     flag(this, 'object', actualDescriptor);
   }
 
   Assertion.addMethod('ownPropertyDescriptor', assertOwnPropertyDescriptor);
   Assertion.addMethod('haveOwnPropertyDescriptor', assertOwnPropertyDescriptor);
 
   /**
    * ### .lengthOf(n[, msg])
    *
    * Asserts that the target's `length` or `size` is equal to the given number
    * `n`.
    *
    *     expect([1, 2, 3]).to.have.lengthOf(3);
    *     expect('foo').to.have.lengthOf(3);
    *     expect(new Set([1, 2, 3])).to.have.lengthOf(3);
    *     expect(new Map([['a', 1], ['b', 2], ['c', 3]])).to.have.lengthOf(3);
    *
    * Add `.not` earlier in the chain to negate `.lengthOf`. However, it's often
    * best to assert that the target's `length` property is equal to its expected
    * value, rather than not equal to one of many unexpected values.
    *
    *     expect('foo').to.have.lengthOf(3); // Recommended
    *     expect('foo').to.not.have.lengthOf(4); // Not recommended
    *
    * `.lengthOf` accepts an optional `msg` argument which is a custom error
    * message to show when the assertion fails. The message can also be given as
    * the second argument to `expect`.
    *
    *     expect([1, 2, 3]).to.have.lengthOf(2, 'nooo why fail??');
    *     expect([1, 2, 3], 'nooo why fail??').to.have.lengthOf(2);
    *
    * `.lengthOf` can also be used as a language chain, causing all `.above`,
    * `.below`, `.least`, `.most`, and `.within` assertions that follow in the
    * chain to use the target's `length` property as the target. However, it's
    * often best to assert that the target's `length` property is equal to its
    * expected length, rather than asserting that its `length` property falls
    * within some range of values.
    *
    *     // Recommended
    *     expect([1, 2, 3]).to.have.lengthOf(3);
    *
    *     // Not recommended
    *     expect([1, 2, 3]).to.have.lengthOf.above(2);
    *     expect([1, 2, 3]).to.have.lengthOf.below(4);
    *     expect([1, 2, 3]).to.have.lengthOf.at.least(3);
    *     expect([1, 2, 3]).to.have.lengthOf.at.most(3);
    *     expect([1, 2, 3]).to.have.lengthOf.within(2,4);
    *
    * Due to a compatibility issue, the alias `.length` can't be chained directly
    * off of an uninvoked method such as `.a`. Therefore, `.length` can't be used
    * interchangeably with `.lengthOf` in every situation. It's recommended to
    * always use `.lengthOf` instead of `.length`.
    *
    *     expect([1, 2, 3]).to.have.a.length(3); // incompatible; throws error
    *     expect([1, 2, 3]).to.have.a.lengthOf(3);  // passes as expected
    *
    * @name lengthOf
    * @alias length
    * @param {Number} n
    * @param {String} msg _optional_
    * @namespace BDD
    * @api public
    */
 
   function assertLengthChain () {
     flag(this, 'doLength', true);
   }
 
   function assertLength (n, msg) {
     if (msg) flag(this, 'message', msg);
     var obj = flag(this, 'object')
       , objType = _.type(obj).toLowerCase()
       , flagMsg = flag(this, 'message')
       , ssfi = flag(this, 'ssfi')
       , descriptor = 'length'
       , itemsCount;
 
     switch (objType) {
       case 'map':
       case 'set':
         descriptor = 'size';
         itemsCount = obj.size;
         break;
       default:
         new Assertion(obj, flagMsg, ssfi, true).to.have.property('length');
         itemsCount = obj.length;
     }
 
     this.assert(
         itemsCount == n
       , 'expected #{this} to have a ' + descriptor + ' of #{exp} but got #{act}'
       , 'expected #{this} to not have a ' + descriptor + ' of #{act}'
       , n
       , itemsCount
     );
   }
 
   Assertion.addChainableMethod('length', assertLength, assertLengthChain);
   Assertion.addChainableMethod('lengthOf', assertLength, assertLengthChain);
 
   /**
    * ### .match(re[, msg])
    *
    * Asserts that the target matches the given regular expression `re`.
    *
    *     expect('foobar').to.match(/^foo/);
    *
    * Add `.not` earlier in the chain to negate `.match`.
    *
    *     expect('foobar').to.not.match(/taco/);
    *
    * `.match` accepts an optional `msg` argument which is a custom error message
    * to show when the assertion fails. The message can also be given as the
    * second argument to `expect`.
    *
    *     expect('foobar').to.match(/taco/, 'nooo why fail??');
    *     expect('foobar', 'nooo why fail??').to.match(/taco/);
    *
    * The alias `.matches` can be used interchangeably with `.match`.
    *
    * @name match
    * @alias matches
    * @param {RegExp} re
    * @param {String} msg _optional_
    * @namespace BDD
    * @api public
    */
   function assertMatch(re, msg) {
     if (msg) flag(this, 'message', msg);
     var obj = flag(this, 'object');
     this.assert(
         re.exec(obj)
       , 'expected #{this} to match ' + re
       , 'expected #{this} not to match ' + re
     );
   }
 
   Assertion.addMethod('match', assertMatch);
   Assertion.addMethod('matches', assertMatch);
 
   /**
    * ### .string(str[, msg])
    *
    * Asserts that the target string contains the given substring `str`.
    *
    *     expect('foobar').to.have.string('bar');
    *
    * Add `.not` earlier in the chain to negate `.string`.
    *
    *     expect('foobar').to.not.have.string('taco');
    *
    * `.string` accepts an optional `msg` argument which is a custom error
    * message to show when the assertion fails. The message can also be given as
    * the second argument to `expect`.
    *
    *     expect('foobar').to.have.string('taco', 'nooo why fail??');
    *     expect('foobar', 'nooo why fail??').to.have.string('taco');
    *
    * @name string
    * @param {String} str
    * @param {String} msg _optional_
    * @namespace BDD
    * @api public
    */
 
   Assertion.addMethod('string', function (str, msg) {
     if (msg) flag(this, 'message', msg);
     var obj = flag(this, 'object')
       , flagMsg = flag(this, 'message')
       , ssfi = flag(this, 'ssfi');
     new Assertion(obj, flagMsg, ssfi, true).is.a('string');
 
     this.assert(
         ~obj.indexOf(str)
       , 'expected #{this} to contain ' + _.inspect(str)
       , 'expected #{this} to not contain ' + _.inspect(str)
     );
   });
 
   /**
    * ### .keys(key1[, key2[, ...]])
    *
    * Asserts that the target object, array, map, or set has the given keys. Only
    * the target's own inherited properties are included in the search.
    *
    * When the target is an object or array, keys can be provided as one or more
    * string arguments, a single array argument, or a single object argument. In
    * the latter case, only the keys in the given object matter; the values are
    * ignored.
    *
    *     expect({a: 1, b: 2}).to.have.all.keys('a', 'b');
    *     expect(['x', 'y']).to.have.all.keys(0, 1);
    *
    *     expect({a: 1, b: 2}).to.have.all.keys(['a', 'b']);
    *     expect(['x', 'y']).to.have.all.keys([0, 1]);
    *
    *     expect({a: 1, b: 2}).to.have.all.keys({a: 4, b: 5}); // ignore 4 and 5
    *     expect(['x', 'y']).to.have.all.keys({0: 4, 1: 5}); // ignore 4 and 5
    *
    * When the target is a map or set, each key must be provided as a separate
    * argument.
    *
    *     expect(new Map([['a', 1], ['b', 2]])).to.have.all.keys('a', 'b');
    *     expect(new Set(['a', 'b'])).to.have.all.keys('a', 'b');
    *
    * Because `.keys` does different things based on the target's type, it's
    * important to check the target's type before using `.keys`. See the `.a` doc
    * for info on testing a target's type.
    *
    *     expect({a: 1, b: 2}).to.be.an('object').that.has.all.keys('a', 'b');
    *
    * By default, strict (`===`) equality is used to compare keys of maps and
    * sets. Add `.deep` earlier in the chain to use deep equality instead. See
    * the `deep-eql` project page for info on the deep equality algorithm:
    * https://github.com/chaijs/deep-eql.
    *
    *     // Target set deeply (but not strictly) has key `{a: 1}`
    *     expect(new Set([{a: 1}])).to.have.all.deep.keys([{a: 1}]);
    *     expect(new Set([{a: 1}])).to.not.have.all.keys([{a: 1}]);
    *
    * By default, the target must have all of the given keys and no more. Add
    * `.any` earlier in the chain to only require that the target have at least
    * one of the given keys. Also, add `.not` earlier in the chain to negate
    * `.keys`. It's often best to add `.any` when negating `.keys`, and to use
    * `.all` when asserting `.keys` without negation.
    *
    * When negating `.keys`, `.any` is preferred because `.not.any.keys` asserts
    * exactly what's expected of the output, whereas `.not.all.keys` creates
    * uncertain expectations.
    *
    *     // Recommended; asserts that target doesn't have any of the given keys
    *     expect({a: 1, b: 2}).to.not.have.any.keys('c', 'd');
    *
    *     // Not recommended; asserts that target doesn't have all of the given
    *     // keys but may or may not have some of them
    *     expect({a: 1, b: 2}).to.not.have.all.keys('c', 'd');
    *
    * When asserting `.keys` without negation, `.all` is preferred because
    * `.all.keys` asserts exactly what's expected of the output, whereas
    * `.any.keys` creates uncertain expectations.
    *
    *     // Recommended; asserts that target has all the given keys
    *     expect({a: 1, b: 2}).to.have.all.keys('a', 'b');
    *
    *     // Not recommended; asserts that target has at least one of the given
    *     // keys but may or may not have more of them
    *     expect({a: 1, b: 2}).to.have.any.keys('a', 'b');
    *
    * Note that `.all` is used by default when neither `.all` nor `.any` appear
    * earlier in the chain. However, it's often best to add `.all` anyway because
    * it improves readability.
    *
    *     // Both assertions are identical
    *     expect({a: 1, b: 2}).to.have.all.keys('a', 'b'); // Recommended
    *     expect({a: 1, b: 2}).to.have.keys('a', 'b'); // Not recommended
    *
    * Add `.include` earlier in the chain to require that the target's keys be a
    * superset of the expected keys, rather than identical sets.
    *
    *     // Target object's keys are a superset of ['a', 'b'] but not identical
    *     expect({a: 1, b: 2, c: 3}).to.include.all.keys('a', 'b');
    *     expect({a: 1, b: 2, c: 3}).to.not.have.all.keys('a', 'b');
    *
    * However, if `.any` and `.include` are combined, only the `.any` takes
    * effect. The `.include` is ignored in this case.
    *
    *     // Both assertions are identical
    *     expect({a: 1}).to.have.any.keys('a', 'b');
    *     expect({a: 1}).to.include.any.keys('a', 'b');
    *
    * A custom error message can be given as the second argument to `expect`.
    *
    *     expect({a: 1}, 'nooo why fail??').to.have.key('b');
    *
    * The alias `.key` can be used interchangeably with `.keys`.
    *
    * @name keys
    * @alias key
    * @param {...String|Array|Object} keys
    * @namespace BDD
    * @api public
    */
 
   function assertKeys (keys) {
     var obj = flag(this, 'object')
       , objType = _.type(obj)
       , keysType = _.type(keys)
       , ssfi = flag(this, 'ssfi')
       , isDeep = flag(this, 'deep')
       , str
       , deepStr = ''
       , actual
       , ok = true
       , flagMsg = flag(this, 'message');
 
     flagMsg = flagMsg ? flagMsg + ': ' : '';
     var mixedArgsMsg = flagMsg + 'when testing keys against an object or an array you must give a single Array|Object|String argument or multiple String arguments';
 
     if (objType === 'Map' || objType === 'Set') {
       deepStr = isDeep ? 'deeply ' : '';
       actual = [];
 
       // Map and Set '.keys' aren't supported in IE 11. Therefore, use .forEach.
       obj.forEach(function (val, key) { actual.push(key) });
 
       if (keysType !== 'Array') {
         keys = Array.prototype.slice.call(arguments);
       }
     } else {
       actual = _.getOwnEnumerableProperties(obj);
 
       switch (keysType) {
         case 'Array':
           if (arguments.length > 1) {
             throw new AssertionError(mixedArgsMsg, undefined, ssfi);
           }
           break;
         case 'Object':
           if (arguments.length > 1) {
             throw new AssertionError(mixedArgsMsg, undefined, ssfi);
           }
           keys = Object.keys(keys);
           break;
         default:
           keys = Array.prototype.slice.call(arguments);
       }
 
       // Only stringify non-Symbols because Symbols would become "Symbol()"
       keys = keys.map(function (val) {
         return typeof val === 'symbol' ? val : String(val);
       });
     }
 
     if (!keys.length) {
       throw new AssertionError(flagMsg + 'keys required', undefined, ssfi);
     }
 
     var len = keys.length
       , any = flag(this, 'any')
       , all = flag(this, 'all')
       , expected = keys;
 
     if (!any && !all) {
       all = true;
     }
 
     // Has any
     if (any) {
       ok = expected.some(function(expectedKey) {
         return actual.some(function(actualKey) {
           if (isDeep) {
             return _.eql(expectedKey, actualKey);
           } else {
             return expectedKey === actualKey;
           }
         });
       });
     }
 
     // Has all
     if (all) {
       ok = expected.every(function(expectedKey) {
         return actual.some(function(actualKey) {
           if (isDeep) {
             return _.eql(expectedKey, actualKey);
           } else {
             return expectedKey === actualKey;
           }
         });
       });
 
       if (!flag(this, 'contains')) {
         ok = ok && keys.length == actual.length;
       }
     }
 
     // Key string
     if (len > 1) {
       keys = keys.map(function(key) {
         return _.inspect(key);
       });
       var last = keys.pop();
       if (all) {
         str = keys.join(', ') + ', and ' + last;
       }
       if (any) {
         str = keys.join(', ') + ', or ' + last;
       }
     } else {
       str = _.inspect(keys[0]);
     }
 
     // Form
     str = (len > 1 ? 'keys ' : 'key ') + str;
 
     // Have / include
     str = (flag(this, 'contains') ? 'contain ' : 'have ') + str;
 
     // Assertion
     this.assert(
         ok
       , 'expected #{this} to ' + deepStr + str
       , 'expected #{this} to not ' + deepStr + str
       , expected.slice(0).sort(_.compareByInspect)
       , actual.sort(_.compareByInspect)
       , true
     );
   }
 
   Assertion.addMethod('keys', assertKeys);
   Assertion.addMethod('key', assertKeys);
 
   /**
    * ### .throw([errorLike], [errMsgMatcher], [msg])
    *
    * When no arguments are provided, `.throw` invokes the target function and
    * asserts that an error is thrown.
    *
    *     var badFn = function () { throw new TypeError('Illegal salmon!'); };
    *
    *     expect(badFn).to.throw();
    *
    * When one argument is provided, and it's an error constructor, `.throw`
    * invokes the target function and asserts that an error is thrown that's an
    * instance of that error constructor.
    *
    *     var badFn = function () { throw new TypeError('Illegal salmon!'); };
    *
    *     expect(badFn).to.throw(TypeError);
    *
    * When one argument is provided, and it's an error instance, `.throw` invokes
    * the target function and asserts that an error is thrown that's strictly
    * (`===`) equal to that error instance.
    *
    *     var err = new TypeError('Illegal salmon!');
    *     var badFn = function () { throw err; };
    *
    *     expect(badFn).to.throw(err);
    *
    * When one argument is provided, and it's a string, `.throw` invokes the
    * target function and asserts that an error is thrown with a message that
    * contains that string.
    *
    *     var badFn = function () { throw new TypeError('Illegal salmon!'); };
    *
    *     expect(badFn).to.throw('salmon');
    *
    * When one argument is provided, and it's a regular expression, `.throw`
    * invokes the target function and asserts that an error is thrown with a
    * message that matches that regular expression.
    *
    *     var badFn = function () { throw new TypeError('Illegal salmon!'); };
    *
    *     expect(badFn).to.throw(/salmon/);
    *
    * When two arguments are provided, and the first is an error instance or
    * constructor, and the second is a string or regular expression, `.throw`
    * invokes the function and asserts that an error is thrown that fulfills both
    * conditions as described above.
    *
    *     var err = new TypeError('Illegal salmon!');
    *     var badFn = function () { throw err; };
    *
    *     expect(badFn).to.throw(TypeError, 'salmon');
    *     expect(badFn).to.throw(TypeError, /salmon/);
    *     expect(badFn).to.throw(err, 'salmon');
    *     expect(badFn).to.throw(err, /salmon/);
    *
    * Add `.not` earlier in the chain to negate `.throw`.
    *
    *     var goodFn = function () {};
    *
    *     expect(goodFn).to.not.throw();
    *
    * However, it's dangerous to negate `.throw` when providing any arguments.
    * The problem is that it creates uncertain expectations by asserting that the
    * target either doesn't throw an error, or that it throws an error but of a
    * different type than the given type, or that it throws an error of the given
    * type but with a message that doesn't include the given string. It's often
    * best to identify the exact output that's expected, and then write an
    * assertion that only accepts that exact output.
    *
    * When the target isn't expected to throw an error, it's often best to assert
    * exactly that.
    *
    *     var goodFn = function () {};
    *
    *     expect(goodFn).to.not.throw(); // Recommended
    *     expect(goodFn).to.not.throw(ReferenceError, 'x'); // Not recommended
    *
    * When the target is expected to throw an error, it's often best to assert
    * that the error is of its expected type, and has a message that includes an
    * expected string, rather than asserting that it doesn't have one of many
    * unexpected types, and doesn't have a message that includes some string.
    *
    *     var badFn = function () { throw new TypeError('Illegal salmon!'); };
    *
    *     expect(badFn).to.throw(TypeError, 'salmon'); // Recommended
    *     expect(badFn).to.not.throw(ReferenceError, 'x'); // Not recommended
    *
    * `.throw` changes the target of any assertions that follow in the chain to
    * be the error object that's thrown.
    *
    *     var err = new TypeError('Illegal salmon!');
    *     err.code = 42;
    *     var badFn = function () { throw err; };
    *
    *     expect(badFn).to.throw(TypeError).with.property('code', 42);
    *
    * `.throw` accepts an optional `msg` argument which is a custom error message
    * to show when the assertion fails. The message can also be given as the
    * second argument to `expect`. When not providing two arguments, always use
    * the second form.
    *
    *     var goodFn = function () {};
    *
    *     expect(goodFn).to.throw(TypeError, 'x', 'nooo why fail??');
    *     expect(goodFn, 'nooo why fail??').to.throw();
    *
    * Due to limitations in ES5, `.throw` may not always work as expected when
    * using a transpiler such as Babel or TypeScript. In particular, it may
    * produce unexpected results when subclassing the built-in `Error` object and
    * then passing the subclassed constructor to `.throw`. See your transpiler's
    * docs for details:
    *
    * - ([Babel](https://babeljs.io/docs/usage/caveats/#classes))
    * - ([TypeScript](https://github.com/Microsoft/TypeScript/wiki/Breaking-Changes#extending-built-ins-like-error-array-and-map-may-no-longer-work))
    *
    * Beware of some common mistakes when using the `throw` assertion. One common
    * mistake is to accidentally invoke the function yourself instead of letting
    * the `throw` assertion invoke the function for you. For example, when
    * testing if a function named `fn` throws, provide `fn` instead of `fn()` as
    * the target for the assertion.
    *
    *     expect(fn).to.throw();     // Good! Tests `fn` as desired
    *     expect(fn()).to.throw();   // Bad! Tests result of `fn()`, not `fn`
    *
    * If you need to assert that your function `fn` throws when passed certain
    * arguments, then wrap a call to `fn` inside of another function.
    *
    *     expect(function () { fn(42); }).to.throw();  // Function expression
    *     expect(() => fn(42)).to.throw();             // ES6 arrow function
    *
    * Another common mistake is to provide an object method (or any stand-alone
    * function that relies on `this`) as the target of the assertion. Doing so is
    * problematic because the `this` context will be lost when the function is
    * invoked by `.throw`; there's no way for it to know what `this` is supposed
    * to be. There are two ways around this problem. One solution is to wrap the
    * method or function call inside of another function. Another solution is to
    * use `bind`.
    *
    *     expect(function () { cat.meow(); }).to.throw();  // Function expression
    *     expect(() => cat.meow()).to.throw();             // ES6 arrow function
    *     expect(cat.meow.bind(cat)).to.throw();           // Bind
    *
    * Finally, it's worth mentioning that it's a best practice in JavaScript to
    * only throw `Error` and derivatives of `Error` such as `ReferenceError`,
    * `TypeError`, and user-defined objects that extend `Error`. No other type of
    * value will generate a stack trace when initialized. With that said, the
    * `throw` assertion does technically support any type of value being thrown,
    * not just `Error` and its derivatives.
    *
    * The aliases `.throws` and `.Throw` can be used interchangeably with
    * `.throw`.
    *
    * @name throw
    * @alias throws
    * @alias Throw
    * @param {Error|ErrorConstructor} errorLike
    * @param {String|RegExp} errMsgMatcher error message
    * @param {String} msg _optional_
    * @see https://developer.mozilla.org/en/JavaScript/Reference/Global_Objects/Error#Error_types
    * @returns error for chaining (null if no error)
    * @namespace BDD
    * @api public
    */
 
   function assertThrows (errorLike, errMsgMatcher, msg) {
     if (msg) flag(this, 'message', msg);
     var obj = flag(this, 'object')
       , ssfi = flag(this, 'ssfi')
       , flagMsg = flag(this, 'message')
       , negate = flag(this, 'negate') || false;
     new Assertion(obj, flagMsg, ssfi, true).is.a('function');
 
     if (errorLike instanceof RegExp || typeof errorLike === 'string') {
       errMsgMatcher = errorLike;
       errorLike = null;
     }
 
     var caughtErr;
     try {
       obj();
     } catch (err) {
       caughtErr = err;
     }
 
     // If we have the negate flag enabled and at least one valid argument it means we do expect an error
     // but we want it to match a given set of criteria
     var everyArgIsUndefined = errorLike === undefined && errMsgMatcher === undefined;
 
     // If we've got the negate flag enabled and both args, we should only fail if both aren't compatible
     // See Issue #551 and PR #683@GitHub
     var everyArgIsDefined = Boolean(errorLike && errMsgMatcher);
     var errorLikeFail = false;
     var errMsgMatcherFail = false;
 
     // Checking if error was thrown
     if (everyArgIsUndefined || !everyArgIsUndefined && !negate) {
       // We need this to display results correctly according to their types
       var errorLikeString = 'an error';
       if (errorLike instanceof Error) {
         errorLikeString = '#{exp}';
       } else if (errorLike) {
         errorLikeString = _.checkError.getConstructorName(errorLike);
       }
 
       this.assert(
           caughtErr
         , 'expected #{this} to throw ' + errorLikeString
         , 'expected #{this} to not throw an error but #{act} was thrown'
         , errorLike && errorLike.toString()
         , (caughtErr instanceof Error ?
             caughtErr.toString() : (typeof caughtErr === 'string' ? caughtErr : caughtErr &&
                                     _.checkError.getConstructorName(caughtErr)))
       );
     }
 
     if (errorLike && caughtErr) {
       // We should compare instances only if `errorLike` is an instance of `Error`
       if (errorLike instanceof Error) {
         var isCompatibleInstance = _.checkError.compatibleInstance(caughtErr, errorLike);
 
         if (isCompatibleInstance === negate) {
           // These checks were created to ensure we won't fail too soon when we've got both args and a negate
           // See Issue #551 and PR #683@GitHub
           if (everyArgIsDefined && negate) {
             errorLikeFail = true;
           } else {
             this.assert(
                 negate
               , 'expected #{this} to throw #{exp} but #{act} was thrown'
               , 'expected #{this} to not throw #{exp}' + (caughtErr && !negate ? ' but #{act} was thrown' : '')
               , errorLike.toString()
               , caughtErr.toString()
             );
           }
         }
       }
 
       var isCompatibleConstructor = _.checkError.compatibleConstructor(caughtErr, errorLike);
       if (isCompatibleConstructor === negate) {
         if (everyArgIsDefined && negate) {
             errorLikeFail = true;
         } else {
           this.assert(
               negate
             , 'expected #{this} to throw #{exp} but #{act} was thrown'
             , 'expected #{this} to not throw #{exp}' + (caughtErr ? ' but #{act} was thrown' : '')
             , (errorLike instanceof Error ? errorLike.toString() : errorLike && _.checkError.getConstructorName(errorLike))
             , (caughtErr instanceof Error ? caughtErr.toString() : caughtErr && _.checkError.getConstructorName(caughtErr))
           );
         }
       }
     }
 
     if (caughtErr && errMsgMatcher !== undefined && errMsgMatcher !== null) {
       // Here we check compatible messages
       var placeholder = 'including';
       if (errMsgMatcher instanceof RegExp) {
         placeholder = 'matching'
       }
 
       var isCompatibleMessage = _.checkError.compatibleMessage(caughtErr, errMsgMatcher);
       if (isCompatibleMessage === negate) {
         if (everyArgIsDefined && negate) {
             errMsgMatcherFail = true;
         } else {
           this.assert(
             negate
             , 'expected #{this} to throw error ' + placeholder + ' #{exp} but got #{act}'
             , 'expected #{this} to throw error not ' + placeholder + ' #{exp}'
             ,  errMsgMatcher
             ,  _.checkError.getMessage(caughtErr)
           );
         }
       }
     }
 
     // If both assertions failed and both should've matched we throw an error
     if (errorLikeFail && errMsgMatcherFail) {
       this.assert(
         negate
         , 'expected #{this} to throw #{exp} but #{act} was thrown'
         , 'expected #{this} to not throw #{exp}' + (caughtErr ? ' but #{act} was thrown' : '')
         , (errorLike instanceof Error ? errorLike.toString() : errorLike && _.checkError.getConstructorName(errorLike))
         , (caughtErr instanceof Error ? caughtErr.toString() : caughtErr && _.checkError.getConstructorName(caughtErr))
       );
     }
 
     flag(this, 'object', caughtErr);
   };
 
   Assertion.addMethod('throw', assertThrows);
   Assertion.addMethod('throws', assertThrows);
   Assertion.addMethod('Throw', assertThrows);
 
   /**
    * ### .respondTo(method[, msg])
    *
    * When the target is a non-function object, `.respondTo` asserts that the
    * target has a method with the given name `method`. The method can be own or
    * inherited, and it can be enumerable or non-enumerable.
    *
    *     function Cat () {}
    *     Cat.prototype.meow = function () {};
    *
    *     expect(new Cat()).to.respondTo('meow');
    *
    * When the target is a function, `.respondTo` asserts that the target's
    * `prototype` property has a method with the given name `method`. Again, the
    * method can be own or inherited, and it can be enumerable or non-enumerable.
    *
    *     function Cat () {}
    *     Cat.prototype.meow = function () {};
    *
    *     expect(Cat).to.respondTo('meow');
    *
    * Add `.itself` earlier in the chain to force `.respondTo` to treat the
    * target as a non-function object, even if it's a function. Thus, it asserts
    * that the target has a method with the given name `method`, rather than
    * asserting that the target's `prototype` property has a method with the
    * given name `method`.
    *
    *     function Cat () {}
    *     Cat.prototype.meow = function () {};
    *     Cat.hiss = function () {};
    *
    *     expect(Cat).itself.to.respondTo('hiss').but.not.respondTo('meow');
    *
    * When not adding `.itself`, it's important to check the target's type before
    * using `.respondTo`. See the `.a` doc for info on checking a target's type.
    *
    *     function Cat () {}
    *     Cat.prototype.meow = function () {};
    *
    *     expect(new Cat()).to.be.an('object').that.respondsTo('meow');
    *
    * Add `.not` earlier in the chain to negate `.respondTo`.
    *
    *     function Dog () {}
    *     Dog.prototype.bark = function () {};
    *
    *     expect(new Dog()).to.not.respondTo('meow');
    *
    * `.respondTo` accepts an optional `msg` argument which is a custom error
    * message to show when the assertion fails. The message can also be given as
    * the second argument to `expect`.
    *
    *     expect({}).to.respondTo('meow', 'nooo why fail??');
    *     expect({}, 'nooo why fail??').to.respondTo('meow');
    *
    * The alias `.respondsTo` can be used interchangeably with `.respondTo`.
    *
    * @name respondTo
    * @alias respondsTo
    * @param {String} method
    * @param {String} msg _optional_
    * @namespace BDD
    * @api public
    */
 
   function respondTo (method, msg) {
     if (msg) flag(this, 'message', msg);
     var obj = flag(this, 'object')
       , itself = flag(this, 'itself')
       , context = ('function' === typeof obj && !itself)
         ? obj.prototype[method]
         : obj[method];
 
     this.assert(
         'function' === typeof context
       , 'expected #{this} to respond to ' + _.inspect(method)
       , 'expected #{this} to not respond to ' + _.inspect(method)
     );
   }
 
   Assertion.addMethod('respondTo', respondTo);
   Assertion.addMethod('respondsTo', respondTo);
 
   /**
    * ### .itself
    *
    * Forces all `.respondTo` assertions that follow in the chain to behave as if
    * the target is a non-function object, even if it's a function. Thus, it
    * causes `.respondTo` to assert that the target has a method with the given
    * name, rather than asserting that the target's `prototype` property has a
    * method with the given name.
    *
    *     function Cat () {}
    *     Cat.prototype.meow = function () {};
    *     Cat.hiss = function () {};
    *
    *     expect(Cat).itself.to.respondTo('hiss').but.not.respondTo('meow');
    *
    * @name itself
    * @namespace BDD
    * @api public
    */
 
   Assertion.addProperty('itself', function () {
     flag(this, 'itself', true);
   });
 
   /**
    * ### .satisfy(matcher[, msg])
    *
    * Invokes the given `matcher` function with the target being passed as the
    * first argument, and asserts that the value returned is truthy.
    *
    *     expect(1).to.satisfy(function(num) {
    *       return num > 0;
    *     });
    *
    * Add `.not` earlier in the chain to negate `.satisfy`.
    *
    *     expect(1).to.not.satisfy(function(num) {
    *       return num > 2;
    *     });
    *
    * `.satisfy` accepts an optional `msg` argument which is a custom error
    * message to show when the assertion fails. The message can also be given as
    * the second argument to `expect`.
    *
    *     expect(1).to.satisfy(function(num) {
    *       return num > 2;
    *     }, 'nooo why fail??');
    *
    *     expect(1, 'nooo why fail??').to.satisfy(function(num) {
    *       return num > 2;
    *     });
    *
    * The alias `.satisfies` can be used interchangeably with `.satisfy`.
    *
    * @name satisfy
    * @alias satisfies
    * @param {Function} matcher
    * @param {String} msg _optional_
    * @namespace BDD
    * @api public
    */
 
   function satisfy (matcher, msg) {
     if (msg) flag(this, 'message', msg);
     var obj = flag(this, 'object');
     var result = matcher(obj);
     this.assert(
         result
       , 'expected #{this} to satisfy ' + _.objDisplay(matcher)
       , 'expected #{this} to not satisfy' + _.objDisplay(matcher)
       , flag(this, 'negate') ? false : true
       , result
     );
   }
 
   Assertion.addMethod('satisfy', satisfy);
   Assertion.addMethod('satisfies', satisfy);
 
   /**
    * ### .closeTo(expected, delta[, msg])
    *
    * Asserts that the target is a number that's within a given +/- `delta` range
    * of the given number `expected`. However, it's often best to assert that the
    * target is equal to its expected value.
    *
    *     // Recommended
    *     expect(1.5).to.equal(1.5);
    *
    *     // Not recommended
    *     expect(1.5).to.be.closeTo(1, 0.5);
    *     expect(1.5).to.be.closeTo(2, 0.5);
    *     expect(1.5).to.be.closeTo(1, 1);
    *
    * Add `.not` earlier in the chain to negate `.closeTo`.
    *
    *     expect(1.5).to.equal(1.5); // Recommended
    *     expect(1.5).to.not.be.closeTo(3, 1); // Not recommended
    *
    * `.closeTo` accepts an optional `msg` argument which is a custom error
    * message to show when the assertion fails. The message can also be given as
    * the second argument to `expect`.
    *
    *     expect(1.5).to.be.closeTo(3, 1, 'nooo why fail??');
    *     expect(1.5, 'nooo why fail??').to.be.closeTo(3, 1);
    *
    * The alias `.approximately` can be used interchangeably with `.closeTo`.
    *
    * @name closeTo
    * @alias approximately
    * @param {Number} expected
    * @param {Number} delta
    * @param {String} msg _optional_
    * @namespace BDD
    * @api public
    */
 
   function closeTo(expected, delta, msg) {
     if (msg) flag(this, 'message', msg);
     var obj = flag(this, 'object')
       , flagMsg = flag(this, 'message')
       , ssfi = flag(this, 'ssfi');
 
     new Assertion(obj, flagMsg, ssfi, true).is.a('number');
     if (typeof expected !== 'number' || typeof delta !== 'number') {
       flagMsg = flagMsg ? flagMsg + ': ' : '';
       var deltaMessage = delta === undefined ? ", and a delta is required" : "";
       throw new AssertionError(
           flagMsg + 'the arguments to closeTo or approximately must be numbers' + deltaMessage,
           undefined,
           ssfi
       );
     }
 
     this.assert(
         Math.abs(obj - expected) <= delta
       , 'expected #{this} to be close to ' + expected + ' +/- ' + delta
       , 'expected #{this} not to be close to ' + expected + ' +/- ' + delta
     );
   }
 
   Assertion.addMethod('closeTo', closeTo);
   Assertion.addMethod('approximately', closeTo);
 
   // Note: Duplicates are ignored if testing for inclusion instead of sameness.
   function isSubsetOf(subset, superset, cmp, contains, ordered) {
     if (!contains) {
       if (subset.length !== superset.length) return false;
       superset = superset.slice();
     }
 
     return subset.every(function(elem, idx) {
       if (ordered) return cmp ? cmp(elem, superset[idx]) : elem === superset[idx];
 
       if (!cmp) {
         var matchIdx = superset.indexOf(elem);
         if (matchIdx === -1) return false;
 
         // Remove match from superset so not counted twice if duplicate in subset.
         if (!contains) superset.splice(matchIdx, 1);
         return true;
       }
 
       return superset.some(function(elem2, matchIdx) {
         if (!cmp(elem, elem2)) return false;
 
         // Remove match from superset so not counted twice if duplicate in subset.
         if (!contains) superset.splice(matchIdx, 1);
         return true;
       });
     });
   }
 
   /**
    * ### .members(set[, msg])
    *
    * Asserts that the target array has the same members as the given array
    * `set`.
    *
    *     expect([1, 2, 3]).to.have.members([2, 1, 3]);
    *     expect([1, 2, 2]).to.have.members([2, 1, 2]);
    *
    * By default, members are compared using strict (`===`) equality. Add `.deep`
    * earlier in the chain to use deep equality instead. See the `deep-eql`
    * project page for info on the deep equality algorithm:
    * https://github.com/chaijs/deep-eql.
    *
    *     // Target array deeply (but not strictly) has member `{a: 1}`
    *     expect([{a: 1}]).to.have.deep.members([{a: 1}]);
    *     expect([{a: 1}]).to.not.have.members([{a: 1}]);
    *
    * By default, order doesn't matter. Add `.ordered` earlier in the chain to
    * require that members appear in the same order.
    *
    *     expect([1, 2, 3]).to.have.ordered.members([1, 2, 3]);
    *     expect([1, 2, 3]).to.have.members([2, 1, 3])
    *       .but.not.ordered.members([2, 1, 3]);
    *
    * By default, both arrays must be the same size. Add `.include` earlier in
    * the chain to require that the target's members be a superset of the
    * expected members. Note that duplicates are ignored in the subset when
    * `.include` is added.
    *
    *     // Target array is a superset of [1, 2] but not identical
    *     expect([1, 2, 3]).to.include.members([1, 2]);
    *     expect([1, 2, 3]).to.not.have.members([1, 2]);
    *
    *     // Duplicates in the subset are ignored
    *     expect([1, 2, 3]).to.include.members([1, 2, 2, 2]);
    *
    * `.deep`, `.ordered`, and `.include` can all be combined. However, if
    * `.include` and `.ordered` are combined, the ordering begins at the start of
    * both arrays.
    *
    *     expect([{a: 1}, {b: 2}, {c: 3}])
    *       .to.include.deep.ordered.members([{a: 1}, {b: 2}])
    *       .but.not.include.deep.ordered.members([{b: 2}, {c: 3}]);
    *
    * Add `.not` earlier in the chain to negate `.members`. However, it's
    * dangerous to do so. The problem is that it creates uncertain expectations
    * by asserting that the target array doesn't have all of the same members as
    * the given array `set` but may or may not have some of them. It's often best
    * to identify the exact output that's expected, and then write an assertion
    * that only accepts that exact output.
    *
    *     expect([1, 2]).to.not.include(3).and.not.include(4); // Recommended
    *     expect([1, 2]).to.not.have.members([3, 4]); // Not recommended
    *
    * `.members` accepts an optional `msg` argument which is a custom error
    * message to show when the assertion fails. The message can also be given as
    * the second argument to `expect`.
    *
    *     expect([1, 2]).to.have.members([1, 2, 3], 'nooo why fail??');
    *     expect([1, 2], 'nooo why fail??').to.have.members([1, 2, 3]);
    *
    * @name members
    * @param {Array} set
    * @param {String} msg _optional_
    * @namespace BDD
    * @api public
    */
 
   Assertion.addMethod('members', function (subset, msg) {
     if (msg) flag(this, 'message', msg);
     var obj = flag(this, 'object')
       , flagMsg = flag(this, 'message')
       , ssfi = flag(this, 'ssfi');
 
     new Assertion(obj, flagMsg, ssfi, true).to.be.an('array');
     new Assertion(subset, flagMsg, ssfi, true).to.be.an('array');
 
     var contains = flag(this, 'contains');
     var ordered = flag(this, 'ordered');
 
     var subject, failMsg, failNegateMsg;
 
     if (contains) {
       subject = ordered ? 'an ordered superset' : 'a superset';
       failMsg = 'expected #{this} to be ' + subject + ' of #{exp}';
       failNegateMsg = 'expected #{this} to not be ' + subject + ' of #{exp}';
     } else {
       subject = ordered ? 'ordered members' : 'members';
       failMsg = 'expected #{this} to have the same ' + subject + ' as #{exp}';
       failNegateMsg = 'expected #{this} to not have the same ' + subject + ' as #{exp}';
     }
 
     var cmp = flag(this, 'deep') ? _.eql : undefined;
 
     this.assert(
         isSubsetOf(subset, obj, cmp, contains, ordered)
       , failMsg
       , failNegateMsg
       , subset
       , obj
       , true
     );
   });
 
   /**
    * ### .oneOf(list[, msg])
    *
    * Asserts that the target is a member of the given array `list`. However,
    * it's often best to assert that the target is equal to its expected value.
    *
    *     expect(1).to.equal(1); // Recommended
    *     expect(1).to.be.oneOf([1, 2, 3]); // Not recommended
    *
    * Comparisons are performed using strict (`===`) equality.
    *
    * Add `.not` earlier in the chain to negate `.oneOf`.
    *
    *     expect(1).to.equal(1); // Recommended
    *     expect(1).to.not.be.oneOf([2, 3, 4]); // Not recommended
    *
    * It can also be chained with `.contain` or `.include`, which will work with
    * both arrays and strings:
    *
    *     expect('Today is sunny').to.contain.oneOf(['sunny', 'cloudy'])
    *     expect('Today is rainy').to.not.contain.oneOf(['sunny', 'cloudy'])
    *     expect([1,2,3]).to.contain.oneOf([3,4,5])
    *     expect([1,2,3]).to.not.contain.oneOf([4,5,6])
    *
    * `.oneOf` accepts an optional `msg` argument which is a custom error message
    * to show when the assertion fails. The message can also be given as the
    * second argument to `expect`.
    *
    *     expect(1).to.be.oneOf([2, 3, 4], 'nooo why fail??');
    *     expect(1, 'nooo why fail??').to.be.oneOf([2, 3, 4]);
    *
    * @name oneOf
    * @param {Array<*>} list
    * @param {String} msg _optional_
    * @namespace BDD
    * @api public
    */
 
   function oneOf (list, msg) {
     if (msg) flag(this, 'message', msg);
     var expected = flag(this, 'object')
       , flagMsg = flag(this, 'message')
       , ssfi = flag(this, 'ssfi')
       , contains = flag(this, 'contains')
       , isDeep = flag(this, 'deep');
     new Assertion(list, flagMsg, ssfi, true).to.be.an('array');
 
     if (contains) {
       this.assert(
         list.some(function(possibility) { return expected.indexOf(possibility) > -1 })
         , 'expected #{this} to contain one of #{exp}'
         , 'expected #{this} to not contain one of #{exp}'
         , list
         , expected
       );
     } else {
       if (isDeep) {
         this.assert(
           list.some(function(possibility) { return _.eql(expected, possibility) })
           , 'expected #{this} to deeply equal one of #{exp}'
           , 'expected #{this} to deeply equal one of #{exp}'
           , list
           , expected
         );
       } else {
         this.assert(
           list.indexOf(expected) > -1
           , 'expected #{this} to be one of #{exp}'
           , 'expected #{this} to not be one of #{exp}'
           , list
           , expected
         );
       }
     }
   }
 
   Assertion.addMethod('oneOf', oneOf);
 
   /**
    * ### .change(subject[, prop[, msg]])
    *
    * When one argument is provided, `.change` asserts that the given function
    * `subject` returns a different value when it's invoked before the target
    * function compared to when it's invoked afterward. However, it's often best
    * to assert that `subject` is equal to its expected value.
    *
    *     var dots = ''
    *       , addDot = function () { dots += '.'; }
    *       , getDots = function () { return dots; };
    *
    *     // Recommended
    *     expect(getDots()).to.equal('');
    *     addDot();
    *     expect(getDots()).to.equal('.');
    *
    *     // Not recommended
    *     expect(addDot).to.change(getDots);
    *
    * When two arguments are provided, `.change` asserts that the value of the
    * given object `subject`'s `prop` property is different before invoking the
    * target function compared to afterward.
    *
    *     var myObj = {dots: ''}
    *       , addDot = function () { myObj.dots += '.'; };
    *
    *     // Recommended
    *     expect(myObj).to.have.property('dots', '');
    *     addDot();
    *     expect(myObj).to.have.property('dots', '.');
    *
    *     // Not recommended
    *     expect(addDot).to.change(myObj, 'dots');
    *
    * Strict (`===`) equality is used to compare before and after values.
    *
    * Add `.not` earlier in the chain to negate `.change`.
    *
    *     var dots = ''
    *       , noop = function () {}
    *       , getDots = function () { return dots; };
    *
    *     expect(noop).to.not.change(getDots);
    *
    *     var myObj = {dots: ''}
    *       , noop = function () {};
    *
    *     expect(noop).to.not.change(myObj, 'dots');
    *
    * `.change` accepts an optional `msg` argument which is a custom error
    * message to show when the assertion fails. The message can also be given as
    * the second argument to `expect`. When not providing two arguments, always
    * use the second form.
    *
    *     var myObj = {dots: ''}
    *       , addDot = function () { myObj.dots += '.'; };
    *
    *     expect(addDot).to.not.change(myObj, 'dots', 'nooo why fail??');
    *
    *     var dots = ''
    *       , addDot = function () { dots += '.'; }
    *       , getDots = function () { return dots; };
    *
    *     expect(addDot, 'nooo why fail??').to.not.change(getDots);
    *
    * `.change` also causes all `.by` assertions that follow in the chain to
    * assert how much a numeric subject was increased or decreased by. However,
    * it's dangerous to use `.change.by`. The problem is that it creates
    * uncertain expectations by asserting that the subject either increases by
    * the given delta, or that it decreases by the given delta. It's often best
    * to identify the exact output that's expected, and then write an assertion
    * that only accepts that exact output.
    *
    *     var myObj = {val: 1}
    *       , addTwo = function () { myObj.val += 2; }
    *       , subtractTwo = function () { myObj.val -= 2; };
    *
    *     expect(addTwo).to.increase(myObj, 'val').by(2); // Recommended
    *     expect(addTwo).to.change(myObj, 'val').by(2); // Not recommended
    *
    *     expect(subtractTwo).to.decrease(myObj, 'val').by(2); // Recommended
    *     expect(subtractTwo).to.change(myObj, 'val').by(2); // Not recommended
    *
    * The alias `.changes` can be used interchangeably with `.change`.
    *
    * @name change
    * @alias changes
    * @param {String} subject
    * @param {String} prop name _optional_
    * @param {String} msg _optional_
    * @namespace BDD
    * @api public
    */
 
   function assertChanges (subject, prop, msg) {
     if (msg) flag(this, 'message', msg);
     var fn = flag(this, 'object')
       , flagMsg = flag(this, 'message')
       , ssfi = flag(this, 'ssfi');
     new Assertion(fn, flagMsg, ssfi, true).is.a('function');
 
     var initial;
     if (!prop) {
       new Assertion(subject, flagMsg, ssfi, true).is.a('function');
       initial = subject();
     } else {
       new Assertion(subject, flagMsg, ssfi, true).to.have.property(prop);
       initial = subject[prop];
     }
 
     fn();
 
     var final = prop === undefined || prop === null ? subject() : subject[prop];
     var msgObj = prop === undefined || prop === null ? initial : '.' + prop;
 
     // This gets flagged because of the .by(delta) assertion
     flag(this, 'deltaMsgObj', msgObj);
     flag(this, 'initialDeltaValue', initial);
     flag(this, 'finalDeltaValue', final);
     flag(this, 'deltaBehavior', 'change');
     flag(this, 'realDelta', final !== initial);
 
     this.assert(
       initial !== final
       , 'expected ' + msgObj + ' to change'
       , 'expected ' + msgObj + ' to not change'
     );
   }
 
   Assertion.addMethod('change', assertChanges);
   Assertion.addMethod('changes', assertChanges);
 
   /**
    * ### .increase(subject[, prop[, msg]])
    *
    * When one argument is provided, `.increase` asserts that the given function
    * `subject` returns a greater number when it's invoked after invoking the
    * target function compared to when it's invoked beforehand. `.increase` also
    * causes all `.by` assertions that follow in the chain to assert how much
    * greater of a number is returned. It's often best to assert that the return
    * value increased by the expected amount, rather than asserting it increased
    * by any amount.
    *
    *     var val = 1
    *       , addTwo = function () { val += 2; }
    *       , getVal = function () { return val; };
    *
    *     expect(addTwo).to.increase(getVal).by(2); // Recommended
    *     expect(addTwo).to.increase(getVal); // Not recommended
    *
    * When two arguments are provided, `.increase` asserts that the value of the
    * given object `subject`'s `prop` property is greater after invoking the
    * target function compared to beforehand.
    *
    *     var myObj = {val: 1}
    *       , addTwo = function () { myObj.val += 2; };
    *
    *     expect(addTwo).to.increase(myObj, 'val').by(2); // Recommended
    *     expect(addTwo).to.increase(myObj, 'val'); // Not recommended
    *
    * Add `.not` earlier in the chain to negate `.increase`. However, it's
    * dangerous to do so. The problem is that it creates uncertain expectations
    * by asserting that the subject either decreases, or that it stays the same.
    * It's often best to identify the exact output that's expected, and then
    * write an assertion that only accepts that exact output.
    *
    * When the subject is expected to decrease, it's often best to assert that it
    * decreased by the expected amount.
    *
    *     var myObj = {val: 1}
    *       , subtractTwo = function () { myObj.val -= 2; };
    *
    *     expect(subtractTwo).to.decrease(myObj, 'val').by(2); // Recommended
    *     expect(subtractTwo).to.not.increase(myObj, 'val'); // Not recommended
    *
    * When the subject is expected to stay the same, it's often best to assert
    * exactly that.
    *
    *     var myObj = {val: 1}
    *       , noop = function () {};
    *
    *     expect(noop).to.not.change(myObj, 'val'); // Recommended
    *     expect(noop).to.not.increase(myObj, 'val'); // Not recommended
    *
    * `.increase` accepts an optional `msg` argument which is a custom error
    * message to show when the assertion fails. The message can also be given as
    * the second argument to `expect`. When not providing two arguments, always
    * use the second form.
    *
    *     var myObj = {val: 1}
    *       , noop = function () {};
    *
    *     expect(noop).to.increase(myObj, 'val', 'nooo why fail??');
    *
    *     var val = 1
    *       , noop = function () {}
    *       , getVal = function () { return val; };
    *
    *     expect(noop, 'nooo why fail??').to.increase(getVal);
    *
    * The alias `.increases` can be used interchangeably with `.increase`.
    *
    * @name increase
    * @alias increases
    * @param {String|Function} subject
    * @param {String} prop name _optional_
    * @param {String} msg _optional_
    * @namespace BDD
    * @api public
    */
 
   function assertIncreases (subject, prop, msg) {
     if (msg) flag(this, 'message', msg);
     var fn = flag(this, 'object')
       , flagMsg = flag(this, 'message')
       , ssfi = flag(this, 'ssfi');
     new Assertion(fn, flagMsg, ssfi, true).is.a('function');
 
     var initial;
     if (!prop) {
       new Assertion(subject, flagMsg, ssfi, true).is.a('function');
       initial = subject();
     } else {
       new Assertion(subject, flagMsg, ssfi, true).to.have.property(prop);
       initial = subject[prop];
     }
 
     // Make sure that the target is a number
     new Assertion(initial, flagMsg, ssfi, true).is.a('number');
 
     fn();
 
     var final = prop === undefined || prop === null ? subject() : subject[prop];
     var msgObj = prop === undefined || prop === null ? initial : '.' + prop;
 
     flag(this, 'deltaMsgObj', msgObj);
     flag(this, 'initialDeltaValue', initial);
     flag(this, 'finalDeltaValue', final);
     flag(this, 'deltaBehavior', 'increase');
     flag(this, 'realDelta', final - initial);
 
     this.assert(
       final - initial > 0
       , 'expected ' + msgObj + ' to increase'
       , 'expected ' + msgObj + ' to not increase'
     );
   }
 
   Assertion.addMethod('increase', assertIncreases);
   Assertion.addMethod('increases', assertIncreases);
 
   /**
    * ### .decrease(subject[, prop[, msg]])
    *
    * When one argument is provided, `.decrease` asserts that the given function
    * `subject` returns a lesser number when it's invoked after invoking the
    * target function compared to when it's invoked beforehand. `.decrease` also
    * causes all `.by` assertions that follow in the chain to assert how much
    * lesser of a number is returned. It's often best to assert that the return
    * value decreased by the expected amount, rather than asserting it decreased
    * by any amount.
    *
    *     var val = 1
    *       , subtractTwo = function () { val -= 2; }
    *       , getVal = function () { return val; };
    *
    *     expect(subtractTwo).to.decrease(getVal).by(2); // Recommended
    *     expect(subtractTwo).to.decrease(getVal); // Not recommended
    *
    * When two arguments are provided, `.decrease` asserts that the value of the
    * given object `subject`'s `prop` property is lesser after invoking the
    * target function compared to beforehand.
    *
    *     var myObj = {val: 1}
    *       , subtractTwo = function () { myObj.val -= 2; };
    *
    *     expect(subtractTwo).to.decrease(myObj, 'val').by(2); // Recommended
    *     expect(subtractTwo).to.decrease(myObj, 'val'); // Not recommended
    *
    * Add `.not` earlier in the chain to negate `.decrease`. However, it's
    * dangerous to do so. The problem is that it creates uncertain expectations
    * by asserting that the subject either increases, or that it stays the same.
    * It's often best to identify the exact output that's expected, and then
    * write an assertion that only accepts that exact output.
    *
    * When the subject is expected to increase, it's often best to assert that it
    * increased by the expected amount.
    *
    *     var myObj = {val: 1}
    *       , addTwo = function () { myObj.val += 2; };
    *
    *     expect(addTwo).to.increase(myObj, 'val').by(2); // Recommended
    *     expect(addTwo).to.not.decrease(myObj, 'val'); // Not recommended
    *
    * When the subject is expected to stay the same, it's often best to assert
    * exactly that.
    *
    *     var myObj = {val: 1}
    *       , noop = function () {};
    *
    *     expect(noop).to.not.change(myObj, 'val'); // Recommended
    *     expect(noop).to.not.decrease(myObj, 'val'); // Not recommended
    *
    * `.decrease` accepts an optional `msg` argument which is a custom error
    * message to show when the assertion fails. The message can also be given as
    * the second argument to `expect`. When not providing two arguments, always
    * use the second form.
    *
    *     var myObj = {val: 1}
    *       , noop = function () {};
    *
    *     expect(noop).to.decrease(myObj, 'val', 'nooo why fail??');
    *
    *     var val = 1
    *       , noop = function () {}
    *       , getVal = function () { return val; };
    *
    *     expect(noop, 'nooo why fail??').to.decrease(getVal);
    *
    * The alias `.decreases` can be used interchangeably with `.decrease`.
    *
    * @name decrease
    * @alias decreases
    * @param {String|Function} subject
    * @param {String} prop name _optional_
    * @param {String} msg _optional_
    * @namespace BDD
    * @api public
    */
 
   function assertDecreases (subject, prop, msg) {
     if (msg) flag(this, 'message', msg);
     var fn = flag(this, 'object')
       , flagMsg = flag(this, 'message')
       , ssfi = flag(this, 'ssfi');
     new Assertion(fn, flagMsg, ssfi, true).is.a('function');
 
     var initial;
     if (!prop) {
       new Assertion(subject, flagMsg, ssfi, true).is.a('function');
       initial = subject();
     } else {
       new Assertion(subject, flagMsg, ssfi, true).to.have.property(prop);
       initial = subject[prop];
     }
 
     // Make sure that the target is a number
     new Assertion(initial, flagMsg, ssfi, true).is.a('number');
 
     fn();
 
     var final = prop === undefined || prop === null ? subject() : subject[prop];
     var msgObj = prop === undefined || prop === null ? initial : '.' + prop;
 
     flag(this, 'deltaMsgObj', msgObj);
     flag(this, 'initialDeltaValue', initial);
     flag(this, 'finalDeltaValue', final);
     flag(this, 'deltaBehavior', 'decrease');
     flag(this, 'realDelta', initial - final);
 
     this.assert(
       final - initial < 0
       , 'expected ' + msgObj + ' to decrease'
       , 'expected ' + msgObj + ' to not decrease'
     );
   }
 
   Assertion.addMethod('decrease', assertDecreases);
   Assertion.addMethod('decreases', assertDecreases);
 
   /**
    * ### .by(delta[, msg])
    *
    * When following an `.increase` assertion in the chain, `.by` asserts that
    * the subject of the `.increase` assertion increased by the given `delta`.
    *
    *     var myObj = {val: 1}
    *       , addTwo = function () { myObj.val += 2; };
    *
    *     expect(addTwo).to.increase(myObj, 'val').by(2);
    *
    * When following a `.decrease` assertion in the chain, `.by` asserts that the
    * subject of the `.decrease` assertion decreased by the given `delta`.
    *
    *     var myObj = {val: 1}
    *       , subtractTwo = function () { myObj.val -= 2; };
    *
    *     expect(subtractTwo).to.decrease(myObj, 'val').by(2);
    *
    * When following a `.change` assertion in the chain, `.by` asserts that the
    * subject of the `.change` assertion either increased or decreased by the
    * given `delta`. However, it's dangerous to use `.change.by`. The problem is
    * that it creates uncertain expectations. It's often best to identify the
    * exact output that's expected, and then write an assertion that only accepts
    * that exact output.
    *
    *     var myObj = {val: 1}
    *       , addTwo = function () { myObj.val += 2; }
    *       , subtractTwo = function () { myObj.val -= 2; };
    *
    *     expect(addTwo).to.increase(myObj, 'val').by(2); // Recommended
    *     expect(addTwo).to.change(myObj, 'val').by(2); // Not recommended
    *
    *     expect(subtractTwo).to.decrease(myObj, 'val').by(2); // Recommended
    *     expect(subtractTwo).to.change(myObj, 'val').by(2); // Not recommended
    *
    * Add `.not` earlier in the chain to negate `.by`. However, it's often best
    * to assert that the subject changed by its expected delta, rather than
    * asserting that it didn't change by one of countless unexpected deltas.
    *
    *     var myObj = {val: 1}
    *       , addTwo = function () { myObj.val += 2; };
    *
    *     // Recommended
    *     expect(addTwo).to.increase(myObj, 'val').by(2);
    *
    *     // Not recommended
    *     expect(addTwo).to.increase(myObj, 'val').but.not.by(3);
    *
    * `.by` accepts an optional `msg` argument which is a custom error message to
    * show when the assertion fails. The message can also be given as the second
    * argument to `expect`.
    *
    *     var myObj = {val: 1}
    *       , addTwo = function () { myObj.val += 2; };
    *
    *     expect(addTwo).to.increase(myObj, 'val').by(3, 'nooo why fail??');
    *     expect(addTwo, 'nooo why fail??').to.increase(myObj, 'val').by(3);
    *
    * @name by
    * @param {Number} delta
    * @param {String} msg _optional_
    * @namespace BDD
    * @api public
    */
 
   function assertDelta(delta, msg) {
     if (msg) flag(this, 'message', msg);
 
     var msgObj = flag(this, 'deltaMsgObj');
     var initial = flag(this, 'initialDeltaValue');
     var final = flag(this, 'finalDeltaValue');
     var behavior = flag(this, 'deltaBehavior');
     var realDelta = flag(this, 'realDelta');
 
     var expression;
     if (behavior === 'change') {
       expression = Math.abs(final - initial) === Math.abs(delta);
     } else {
       expression = realDelta === Math.abs(delta);
     }
 
     this.assert(
       expression
       , 'expected ' + msgObj + ' to ' + behavior + ' by ' + delta
       , 'expected ' + msgObj + ' to not ' + behavior + ' by ' + delta
     );
   }
 
   Assertion.addMethod('by', assertDelta);
 
   /**
    * ### .extensible
    *
    * Asserts that the target is extensible, which means that new properties can
    * be added to it. Primitives are never extensible.
    *
    *     expect({a: 1}).to.be.extensible;
    *
    * Add `.not` earlier in the chain to negate `.extensible`.
    *
    *     var nonExtensibleObject = Object.preventExtensions({})
    *       , sealedObject = Object.seal({})
    *       , frozenObject = Object.freeze({});
    *
    *     expect(nonExtensibleObject).to.not.be.extensible;
    *     expect(sealedObject).to.not.be.extensible;
    *     expect(frozenObject).to.not.be.extensible;
    *     expect(1).to.not.be.extensible;
    *
    * A custom error message can be given as the second argument to `expect`.
    *
    *     expect(1, 'nooo why fail??').to.be.extensible;
    *
    * @name extensible
    * @namespace BDD
    * @api public
    */
 
   Assertion.addProperty('extensible', function() {
     var obj = flag(this, 'object');
 
     // In ES5, if the argument to this method is a primitive, then it will cause a TypeError.
     // In ES6, a non-object argument will be treated as if it was a non-extensible ordinary object, simply return false.
     // https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/Object/isExtensible
     // The following provides ES6 behavior for ES5 environments.
 
     var isExtensible = obj === Object(obj) && Object.isExtensible(obj);
 
     this.assert(
       isExtensible
       , 'expected #{this} to be extensible'
       , 'expected #{this} to not be extensible'
     );
   });
 
   /**
    * ### .sealed
    *
    * Asserts that the target is sealed, which means that new properties can't be
    * added to it, and its existing properties can't be reconfigured or deleted.
    * However, it's possible that its existing properties can still be reassigned
    * to different values. Primitives are always sealed.
    *
    *     var sealedObject = Object.seal({});
    *     var frozenObject = Object.freeze({});
    *
    *     expect(sealedObject).to.be.sealed;
    *     expect(frozenObject).to.be.sealed;
    *     expect(1).to.be.sealed;
    *
    * Add `.not` earlier in the chain to negate `.sealed`.
    *
    *     expect({a: 1}).to.not.be.sealed;
    *
    * A custom error message can be given as the second argument to `expect`.
    *
    *     expect({a: 1}, 'nooo why fail??').to.be.sealed;
    *
    * @name sealed
    * @namespace BDD
    * @api public
    */
 
   Assertion.addProperty('sealed', function() {
     var obj = flag(this, 'object');
 
     // In ES5, if the argument to this method is a primitive, then it will cause a TypeError.
     // In ES6, a non-object argument will be treated as if it was a sealed ordinary object, simply return true.
     // See https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/Object/isSealed
     // The following provides ES6 behavior for ES5 environments.
 
     var isSealed = obj === Object(obj) ? Object.isSealed(obj) : true;
 
     this.assert(
       isSealed
       , 'expected #{this} to be sealed'
       , 'expected #{this} to not be sealed'
     );
   });
 
   /**
    * ### .frozen
    *
    * Asserts that the target is frozen, which means that new properties can't be
    * added to it, and its existing properties can't be reassigned to different
    * values, reconfigured, or deleted. Primitives are always frozen.
    *
    *     var frozenObject = Object.freeze({});
    *
    *     expect(frozenObject).to.be.frozen;
    *     expect(1).to.be.frozen;
    *
    * Add `.not` earlier in the chain to negate `.frozen`.
    *
    *     expect({a: 1}).to.not.be.frozen;
    *
    * A custom error message can be given as the second argument to `expect`.
    *
    *     expect({a: 1}, 'nooo why fail??').to.be.frozen;
    *
    * @name frozen
    * @namespace BDD
    * @api public
    */
 
   Assertion.addProperty('frozen', function() {
     var obj = flag(this, 'object');
 
     // In ES5, if the argument to this method is a primitive, then it will cause a TypeError.
     // In ES6, a non-object argument will be treated as if it was a frozen ordinary object, simply return true.
     // See https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/Object/isFrozen
     // The following provides ES6 behavior for ES5 environments.
 
     var isFrozen = obj === Object(obj) ? Object.isFrozen(obj) : true;
 
     this.assert(
       isFrozen
       , 'expected #{this} to be frozen'
       , 'expected #{this} to not be frozen'
     );
   });
 
   /**
    * ### .finite
    *
    * Asserts that the target is a number, and isn't `NaN` or positive/negative
    * `Infinity`.
    *
    *     expect(1).to.be.finite;
    *
    * Add `.not` earlier in the chain to negate `.finite`. However, it's
    * dangerous to do so. The problem is that it creates uncertain expectations
    * by asserting that the subject either isn't a number, or that it's `NaN`, or
    * that it's positive `Infinity`, or that it's negative `Infinity`. It's often
    * best to identify the exact output that's expected, and then write an
    * assertion that only accepts that exact output.
    *
    * When the target isn't expected to be a number, it's often best to assert
    * that it's the expected type, rather than asserting that it isn't one of
    * many unexpected types.
    *
    *     expect('foo').to.be.a('string'); // Recommended
    *     expect('foo').to.not.be.finite; // Not recommended
    *
    * When the target is expected to be `NaN`, it's often best to assert exactly
    * that.
    *
    *     expect(NaN).to.be.NaN; // Recommended
    *     expect(NaN).to.not.be.finite; // Not recommended
    *
    * When the target is expected to be positive infinity, it's often best to
    * assert exactly that.
    *
    *     expect(Infinity).to.equal(Infinity); // Recommended
    *     expect(Infinity).to.not.be.finite; // Not recommended
    *
    * When the target is expected to be negative infinity, it's often best to
    * assert exactly that.
    *
    *     expect(-Infinity).to.equal(-Infinity); // Recommended
    *     expect(-Infinity).to.not.be.finite; // Not recommended
    *
    * A custom error message can be given as the second argument to `expect`.
    *
    *     expect('foo', 'nooo why fail??').to.be.finite;
    *
    * @name finite
    * @namespace BDD
    * @api public
    */
 
   Assertion.addProperty('finite', function(msg) {
     var obj = flag(this, 'object');
 
     this.assert(
         typeof obj === 'number' && isFinite(obj)
       , 'expected #{this} to be a finite number'
       , 'expected #{this} to not be a finite number'
     );
   });
 };
 
 },{}],6:[function(require,module,exports){
 /*!
  * chai
  * Copyright(c) 2011-2014 Jake Luer <jake@alogicalparadox.com>
  * MIT Licensed
  */
 
 module.exports = function (chai, util) {
   /*!
    * Chai dependencies.
    */
 
   var Assertion = chai.Assertion
     , flag = util.flag;
 
   /*!
    * Module export.
    */
 
   /**
    * ### assert(expression, message)
    *
    * Write your own test expressions.
    *
    *     assert('foo' !== 'bar', 'foo is not bar');
    *     assert(Array.isArray([]), 'empty arrays are arrays');
    *
    * @param {Mixed} expression to test for truthiness
    * @param {String} message to display on error
    * @name assert
    * @namespace Assert
    * @api public
    */
 
   var assert = chai.assert = function (express, errmsg) {
     var test = new Assertion(null, null, chai.assert, true);
     test.assert(
         express
       , errmsg
       , '[ negation message unavailable ]'
     );
   };
 
   /**
    * ### .fail([message])
    * ### .fail(actual, expected, [message], [operator])
    *
    * Throw a failure. Node.js `assert` module-compatible.
    *
    *     assert.fail();
    *     assert.fail("custom error message");
    *     assert.fail(1, 2);
    *     assert.fail(1, 2, "custom error message");
    *     assert.fail(1, 2, "custom error message", ">");
    *     assert.fail(1, 2, undefined, ">");
    *
    * @name fail
    * @param {Mixed} actual
    * @param {Mixed} expected
    * @param {String} message
    * @param {String} operator
    * @namespace Assert
    * @api public
    */
 
   assert.fail = function (actual, expected, message, operator) {
     if (arguments.length < 2) {
         // Comply with Node's fail([message]) interface
 
         message = actual;
         actual = undefined;
     }
 
     message = message || 'assert.fail()';
     throw new chai.AssertionError(message, {
         actual: actual
       , expected: expected
       , operator: operator
     }, assert.fail);
   };
 
   /**
    * ### .isOk(object, [message])
    *
    * Asserts that `object` is truthy.
    *
    *     assert.isOk('everything', 'everything is ok');
    *     assert.isOk(false, 'this will fail');
    *
    * @name isOk
    * @alias ok
    * @param {Mixed} object to test
    * @param {String} message
    * @namespace Assert
    * @api public
    */
 
   assert.isOk = function (val, msg) {
     new Assertion(val, msg, assert.isOk, true).is.ok;
   };
 
   /**
    * ### .isNotOk(object, [message])
    *
    * Asserts that `object` is falsy.
    *
    *     assert.isNotOk('everything', 'this will fail');
    *     assert.isNotOk(false, 'this will pass');
    *
    * @name isNotOk
    * @alias notOk
    * @param {Mixed} object to test
    * @param {String} message
    * @namespace Assert
    * @api public
    */
 
   assert.isNotOk = function (val, msg) {
     new Assertion(val, msg, assert.isNotOk, true).is.not.ok;
   };
 
   /**
    * ### .equal(actual, expected, [message])
    *
    * Asserts non-strict equality (`==`) of `actual` and `expected`.
    *
    *     assert.equal(3, '3', '== coerces values to strings');
    *
    * @name equal
    * @param {Mixed} actual
    * @param {Mixed} expected
    * @param {String} message
    * @namespace Assert
    * @api public
    */
 
   assert.equal = function (act, exp, msg) {
     var test = new Assertion(act, msg, assert.equal, true);
 
     test.assert(
         exp == flag(test, 'object')
       , 'expected #{this} to equal #{exp}'
       , 'expected #{this} to not equal #{act}'
       , exp
       , act
       , true
     );
   };
 
   /**
    * ### .notEqual(actual, expected, [message])
    *
    * Asserts non-strict inequality (`!=`) of `actual` and `expected`.
    *
    *     assert.notEqual(3, 4, 'these numbers are not equal');
    *
    * @name notEqual
    * @param {Mixed} actual
    * @param {Mixed} expected
    * @param {String} message
    * @namespace Assert
    * @api public
    */
 
   assert.notEqual = function (act, exp, msg) {
     var test = new Assertion(act, msg, assert.notEqual, true);
 
     test.assert(
         exp != flag(test, 'object')
       , 'expected #{this} to not equal #{exp}'
       , 'expected #{this} to equal #{act}'
       , exp
       , act
       , true
     );
   };
 
   /**
    * ### .strictEqual(actual, expected, [message])
    *
    * Asserts strict equality (`===`) of `actual` and `expected`.
    *
    *     assert.strictEqual(true, true, 'these booleans are strictly equal');
    *
    * @name strictEqual
    * @param {Mixed} actual
    * @param {Mixed} expected
    * @param {String} message
    * @namespace Assert
    * @api public
    */
 
   assert.strictEqual = function (act, exp, msg) {
     new Assertion(act, msg, assert.strictEqual, true).to.equal(exp);
   };
 
   /**
    * ### .notStrictEqual(actual, expected, [message])
    *
    * Asserts strict inequality (`!==`) of `actual` and `expected`.
    *
    *     assert.notStrictEqual(3, '3', 'no coercion for strict equality');
    *
    * @name notStrictEqual
    * @param {Mixed} actual
    * @param {Mixed} expected
    * @param {String} message
    * @namespace Assert
    * @api public
    */
 
   assert.notStrictEqual = function (act, exp, msg) {
     new Assertion(act, msg, assert.notStrictEqual, true).to.not.equal(exp);
   };
 
   /**
    * ### .deepEqual(actual, expected, [message])
    *
    * Asserts that `actual` is deeply equal to `expected`.
    *
    *     assert.deepEqual({ tea: 'green' }, { tea: 'green' });
    *
    * @name deepEqual
    * @param {Mixed} actual
    * @param {Mixed} expected
    * @param {String} message
    * @alias deepStrictEqual
    * @namespace Assert
    * @api public
    */
 
   assert.deepEqual = assert.deepStrictEqual = function (act, exp, msg) {
     new Assertion(act, msg, assert.deepEqual, true).to.eql(exp);
   };
 
   /**
    * ### .notDeepEqual(actual, expected, [message])
    *
    * Assert that `actual` is not deeply equal to `expected`.
    *
    *     assert.notDeepEqual({ tea: 'green' }, { tea: 'jasmine' });
    *
    * @name notDeepEqual
    * @param {Mixed} actual
    * @param {Mixed} expected
    * @param {String} message
    * @namespace Assert
    * @api public
    */
 
   assert.notDeepEqual = function (act, exp, msg) {
     new Assertion(act, msg, assert.notDeepEqual, true).to.not.eql(exp);
   };
 
    /**
    * ### .isAbove(valueToCheck, valueToBeAbove, [message])
    *
    * Asserts `valueToCheck` is strictly greater than (>) `valueToBeAbove`.
    *
    *     assert.isAbove(5, 2, '5 is strictly greater than 2');
    *
    * @name isAbove
    * @param {Mixed} valueToCheck
    * @param {Mixed} valueToBeAbove
    * @param {String} message
    * @namespace Assert
    * @api public
    */
 
   assert.isAbove = function (val, abv, msg) {
     new Assertion(val, msg, assert.isAbove, true).to.be.above(abv);
   };
 
    /**
    * ### .isAtLeast(valueToCheck, valueToBeAtLeast, [message])
    *
    * Asserts `valueToCheck` is greater than or equal to (>=) `valueToBeAtLeast`.
    *
    *     assert.isAtLeast(5, 2, '5 is greater or equal to 2');
    *     assert.isAtLeast(3, 3, '3 is greater or equal to 3');
    *
    * @name isAtLeast
    * @param {Mixed} valueToCheck
    * @param {Mixed} valueToBeAtLeast
    * @param {String} message
    * @namespace Assert
    * @api public
    */
 
   assert.isAtLeast = function (val, atlst, msg) {
     new Assertion(val, msg, assert.isAtLeast, true).to.be.least(atlst);
   };
 
    /**
    * ### .isBelow(valueToCheck, valueToBeBelow, [message])
    *
    * Asserts `valueToCheck` is strictly less than (<) `valueToBeBelow`.
    *
    *     assert.isBelow(3, 6, '3 is strictly less than 6');
    *
    * @name isBelow
    * @param {Mixed} valueToCheck
    * @param {Mixed} valueToBeBelow
    * @param {String} message
    * @namespace Assert
    * @api public
    */
 
   assert.isBelow = function (val, blw, msg) {
     new Assertion(val, msg, assert.isBelow, true).to.be.below(blw);
   };
 
    /**
    * ### .isAtMost(valueToCheck, valueToBeAtMost, [message])
    *
    * Asserts `valueToCheck` is less than or equal to (<=) `valueToBeAtMost`.
    *
    *     assert.isAtMost(3, 6, '3 is less than or equal to 6');
    *     assert.isAtMost(4, 4, '4 is less than or equal to 4');
    *
    * @name isAtMost
    * @param {Mixed} valueToCheck
    * @param {Mixed} valueToBeAtMost
    * @param {String} message
    * @namespace Assert
    * @api public
    */
 
   assert.isAtMost = function (val, atmst, msg) {
     new Assertion(val, msg, assert.isAtMost, true).to.be.most(atmst);
   };
 
   /**
    * ### .isTrue(value, [message])
    *
    * Asserts that `value` is true.
    *
    *     var teaServed = true;
    *     assert.isTrue(teaServed, 'the tea has been served');
    *
    * @name isTrue
    * @param {Mixed} value
    * @param {String} message
    * @namespace Assert
    * @api public
    */
 
   assert.isTrue = function (val, msg) {
     new Assertion(val, msg, assert.isTrue, true).is['true'];
   };
 
   /**
    * ### .isNotTrue(value, [message])
    *
    * Asserts that `value` is not true.
    *
    *     var tea = 'tasty chai';
    *     assert.isNotTrue(tea, 'great, time for tea!');
    *
    * @name isNotTrue
    * @param {Mixed} value
    * @param {String} message
    * @namespace Assert
    * @api public
    */
 
   assert.isNotTrue = function (val, msg) {
     new Assertion(val, msg, assert.isNotTrue, true).to.not.equal(true);
   };
 
   /**
    * ### .isFalse(value, [message])
    *
    * Asserts that `value` is false.
    *
    *     var teaServed = false;
    *     assert.isFalse(teaServed, 'no tea yet? hmm...');
    *
    * @name isFalse
    * @param {Mixed} value
    * @param {String} message
    * @namespace Assert
    * @api public
    */
 
   assert.isFalse = function (val, msg) {
     new Assertion(val, msg, assert.isFalse, true).is['false'];
   };
 
   /**
    * ### .isNotFalse(value, [message])
    *
    * Asserts that `value` is not false.
    *
    *     var tea = 'tasty chai';
    *     assert.isNotFalse(tea, 'great, time for tea!');
    *
    * @name isNotFalse
    * @param {Mixed} value
    * @param {String} message
    * @namespace Assert
    * @api public
    */
 
   assert.isNotFalse = function (val, msg) {
     new Assertion(val, msg, assert.isNotFalse, true).to.not.equal(false);
   };
 
   /**
    * ### .isNull(value, [message])
    *
    * Asserts that `value` is null.
    *
    *     assert.isNull(err, 'there was no error');
    *
    * @name isNull
    * @param {Mixed} value
    * @param {String} message
    * @namespace Assert
    * @api public
    */
 
   assert.isNull = function (val, msg) {
     new Assertion(val, msg, assert.isNull, true).to.equal(null);
   };
 
   /**
    * ### .isNotNull(value, [message])
    *
    * Asserts that `value` is not null.
    *
    *     var tea = 'tasty chai';
    *     assert.isNotNull(tea, 'great, time for tea!');
    *
    * @name isNotNull
    * @param {Mixed} value
    * @param {String} message
    * @namespace Assert
    * @api public
    */
 
   assert.isNotNull = function (val, msg) {
     new Assertion(val, msg, assert.isNotNull, true).to.not.equal(null);
   };
 
   /**
    * ### .isNaN
    *
    * Asserts that value is NaN.
    *
    *     assert.isNaN(NaN, 'NaN is NaN');
    *
    * @name isNaN
    * @param {Mixed} value
    * @param {String} message
    * @namespace Assert
    * @api public
    */
 
   assert.isNaN = function (val, msg) {
     new Assertion(val, msg, assert.isNaN, true).to.be.NaN;
   };
 
   /**
    * ### .isNotNaN
    *
    * Asserts that value is not NaN.
    *
    *     assert.isNotNaN(4, '4 is not NaN');
    *
    * @name isNotNaN
    * @param {Mixed} value
    * @param {String} message
    * @namespace Assert
    * @api public
    */
   assert.isNotNaN = function (val, msg) {
     new Assertion(val, msg, assert.isNotNaN, true).not.to.be.NaN;
   };
 
   /**
    * ### .exists
    *
    * Asserts that the target is neither `null` nor `undefined`.
    *
    *     var foo = 'hi';
    *
    *     assert.exists(foo, 'foo is neither `null` nor `undefined`');
    *
    * @name exists
    * @param {Mixed} value
    * @param {String} message
    * @namespace Assert
    * @api public
    */
 
   assert.exists = function (val, msg) {
     new Assertion(val, msg, assert.exists, true).to.exist;
   };
 
   /**
    * ### .notExists
    *
    * Asserts that the target is either `null` or `undefined`.
    *
    *     var bar = null
    *       , baz;
    *
    *     assert.notExists(bar);
    *     assert.notExists(baz, 'baz is either null or undefined');
    *
    * @name notExists
    * @param {Mixed} value
    * @param {String} message
    * @namespace Assert
    * @api public
    */
 
   assert.notExists = function (val, msg) {
     new Assertion(val, msg, assert.notExists, true).to.not.exist;
   };
 
   /**
    * ### .isUndefined(value, [message])
    *
    * Asserts that `value` is `undefined`.
    *
    *     var tea;
    *     assert.isUndefined(tea, 'no tea defined');
    *
    * @name isUndefined
    * @param {Mixed} value
    * @param {String} message
    * @namespace Assert
    * @api public
    */
 
   assert.isUndefined = function (val, msg) {
     new Assertion(val, msg, assert.isUndefined, true).to.equal(undefined);
   };
 
   /**
    * ### .isDefined(value, [message])
    *
    * Asserts that `value` is not `undefined`.
    *
    *     var tea = 'cup of chai';
    *     assert.isDefined(tea, 'tea has been defined');
    *
    * @name isDefined
    * @param {Mixed} value
    * @param {String} message
    * @namespace Assert
    * @api public
    */
 
   assert.isDefined = function (val, msg) {
     new Assertion(val, msg, assert.isDefined, true).to.not.equal(undefined);
   };
 
   /**
    * ### .isFunction(value, [message])
    *
    * Asserts that `value` is a function.
    *
    *     function serveTea() { return 'cup of tea'; };
    *     assert.isFunction(serveTea, 'great, we can have tea now');
    *
    * @name isFunction
    * @param {Mixed} value
    * @param {String} message
    * @namespace Assert
    * @api public
    */
 
   assert.isFunction = function (val, msg) {
     new Assertion(val, msg, assert.isFunction, true).to.be.a('function');
   };
 
   /**
    * ### .isNotFunction(value, [message])
    *
    * Asserts that `value` is _not_ a function.
    *
    *     var serveTea = [ 'heat', 'pour', 'sip' ];
    *     assert.isNotFunction(serveTea, 'great, we have listed the steps');
    *
    * @name isNotFunction
    * @param {Mixed} value
    * @param {String} message
    * @namespace Assert
    * @api public
    */
 
   assert.isNotFunction = function (val, msg) {
     new Assertion(val, msg, assert.isNotFunction, true).to.not.be.a('function');
   };
 
   /**
    * ### .isObject(value, [message])
    *
    * Asserts that `value` is an object of type 'Object' (as revealed by `Object.prototype.toString`).
    * _The assertion does not match subclassed objects._
    *
    *     var selection = { name: 'Chai', serve: 'with spices' };
    *     assert.isObject(selection, 'tea selection is an object');
    *
    * @name isObject
    * @param {Mixed} value
    * @param {String} message
    * @namespace Assert
    * @api public
    */
 
   assert.isObject = function (val, msg) {
     new Assertion(val, msg, assert.isObject, true).to.be.a('object');
   };
 
   /**
    * ### .isNotObject(value, [message])
    *
    * Asserts that `value` is _not_ an object of type 'Object' (as revealed by `Object.prototype.toString`).
    *
    *     var selection = 'chai'
    *     assert.isNotObject(selection, 'tea selection is not an object');
    *     assert.isNotObject(null, 'null is not an object');
    *
    * @name isNotObject
    * @param {Mixed} value
    * @param {String} message
    * @namespace Assert
    * @api public
    */
 
   assert.isNotObject = function (val, msg) {
     new Assertion(val, msg, assert.isNotObject, true).to.not.be.a('object');
   };
 
   /**
    * ### .isArray(value, [message])
    *
    * Asserts that `value` is an array.
    *
    *     var menu = [ 'green', 'chai', 'oolong' ];
    *     assert.isArray(menu, 'what kind of tea do we want?');
    *
    * @name isArray
    * @param {Mixed} value
    * @param {String} message
    * @namespace Assert
    * @api public
    */
 
   assert.isArray = function (val, msg) {
     new Assertion(val, msg, assert.isArray, true).to.be.an('array');
   };
 
   /**
    * ### .isNotArray(value, [message])
    *
    * Asserts that `value` is _not_ an array.
    *
    *     var menu = 'green|chai|oolong';
    *     assert.isNotArray(menu, 'what kind of tea do we want?');
    *
    * @name isNotArray
    * @param {Mixed} value
    * @param {String} message
    * @namespace Assert
    * @api public
    */
 
   assert.isNotArray = function (val, msg) {
     new Assertion(val, msg, assert.isNotArray, true).to.not.be.an('array');
   };
 
   /**
    * ### .isString(value, [message])
    *
    * Asserts that `value` is a string.
    *
    *     var teaOrder = 'chai';
    *     assert.isString(teaOrder, 'order placed');
    *
    * @name isString
    * @param {Mixed} value
    * @param {String} message
    * @namespace Assert
    * @api public
    */
 
   assert.isString = function (val, msg) {
     new Assertion(val, msg, assert.isString, true).to.be.a('string');
   };
 
   /**
    * ### .isNotString(value, [message])
    *
    * Asserts that `value` is _not_ a string.
    *
    *     var teaOrder = 4;
    *     assert.isNotString(teaOrder, 'order placed');
    *
    * @name isNotString
    * @param {Mixed} value
    * @param {String} message
    * @namespace Assert
    * @api public
    */
 
   assert.isNotString = function (val, msg) {
     new Assertion(val, msg, assert.isNotString, true).to.not.be.a('string');
   };
 
   /**
    * ### .isNumber(value, [message])
    *
    * Asserts that `value` is a number.
    *
    *     var cups = 2;
    *     assert.isNumber(cups, 'how many cups');
    *
    * @name isNumber
    * @param {Number} value
    * @param {String} message
    * @namespace Assert
    * @api public
    */
 
   assert.isNumber = function (val, msg) {
     new Assertion(val, msg, assert.isNumber, true).to.be.a('number');
   };
 
   /**
    * ### .isNotNumber(value, [message])
    *
    * Asserts that `value` is _not_ a number.
    *
    *     var cups = '2 cups please';
    *     assert.isNotNumber(cups, 'how many cups');
    *
    * @name isNotNumber
    * @param {Mixed} value
    * @param {String} message
    * @namespace Assert
    * @api public
    */
 
   assert.isNotNumber = function (val, msg) {
     new Assertion(val, msg, assert.isNotNumber, true).to.not.be.a('number');
   };
 
    /**
    * ### .isFinite(value, [message])
    *
    * Asserts that `value` is a finite number. Unlike `.isNumber`, this will fail for `NaN` and `Infinity`.
    *
    *     var cups = 2;
    *     assert.isFinite(cups, 'how many cups');
    *
    *     assert.isFinite(NaN); // throws
    *
    * @name isFinite
    * @param {Number} value
    * @param {String} message
    * @namespace Assert
    * @api public
    */
 
   assert.isFinite = function (val, msg) {
     new Assertion(val, msg, assert.isFinite, true).to.be.finite;
   };
 
   /**
    * ### .isBoolean(value, [message])
    *
    * Asserts that `value` is a boolean.
    *
    *     var teaReady = true
    *       , teaServed = false;
    *
    *     assert.isBoolean(teaReady, 'is the tea ready');
    *     assert.isBoolean(teaServed, 'has tea been served');
    *
    * @name isBoolean
    * @param {Mixed} value
    * @param {String} message
    * @namespace Assert
    * @api public
    */
 
   assert.isBoolean = function (val, msg) {
     new Assertion(val, msg, assert.isBoolean, true).to.be.a('boolean');
   };
 
   /**
    * ### .isNotBoolean(value, [message])
    *
    * Asserts that `value` is _not_ a boolean.
    *
    *     var teaReady = 'yep'
    *       , teaServed = 'nope';
    *
    *     assert.isNotBoolean(teaReady, 'is the tea ready');
    *     assert.isNotBoolean(teaServed, 'has tea been served');
    *
    * @name isNotBoolean
    * @param {Mixed} value
    * @param {String} message
    * @namespace Assert
    * @api public
    */
 
   assert.isNotBoolean = function (val, msg) {
     new Assertion(val, msg, assert.isNotBoolean, true).to.not.be.a('boolean');
   };
 
   /**
    * ### .typeOf(value, name, [message])
    *
    * Asserts that `value`'s type is `name`, as determined by
    * `Object.prototype.toString`.
    *
    *     assert.typeOf({ tea: 'chai' }, 'object', 'we have an object');
    *     assert.typeOf(['chai', 'jasmine'], 'array', 'we have an array');
    *     assert.typeOf('tea', 'string', 'we have a string');
    *     assert.typeOf(/tea/, 'regexp', 'we have a regular expression');
    *     assert.typeOf(null, 'null', 'we have a null');
    *     assert.typeOf(undefined, 'undefined', 'we have an undefined');
    *
    * @name typeOf
    * @param {Mixed} value
    * @param {String} name
    * @param {String} message
    * @namespace Assert
    * @api public
    */
 
   assert.typeOf = function (val, type, msg) {
     new Assertion(val, msg, assert.typeOf, true).to.be.a(type);
   };
 
   /**
    * ### .notTypeOf(value, name, [message])
    *
    * Asserts that `value`'s type is _not_ `name`, as determined by
    * `Object.prototype.toString`.
    *
    *     assert.notTypeOf('tea', 'number', 'strings are not numbers');
    *
    * @name notTypeOf
    * @param {Mixed} value
    * @param {String} typeof name
    * @param {String} message
    * @namespace Assert
    * @api public
    */
 
   assert.notTypeOf = function (val, type, msg) {
     new Assertion(val, msg, assert.notTypeOf, true).to.not.be.a(type);
   };
 
   /**
    * ### .instanceOf(object, constructor, [message])
    *
    * Asserts that `value` is an instance of `constructor`.
    *
    *     var Tea = function (name) { this.name = name; }
    *       , chai = new Tea('chai');
    *
    *     assert.instanceOf(chai, Tea, 'chai is an instance of tea');
    *
    * @name instanceOf
    * @param {Object} object
    * @param {Constructor} constructor
    * @param {String} message
    * @namespace Assert
    * @api public
    */
 
   assert.instanceOf = function (val, type, msg) {
     new Assertion(val, msg, assert.instanceOf, true).to.be.instanceOf(type);
   };
 
   /**
    * ### .notInstanceOf(object, constructor, [message])
    *
    * Asserts `value` is not an instance of `constructor`.
    *
    *     var Tea = function (name) { this.name = name; }
    *       , chai = new String('chai');
    *
    *     assert.notInstanceOf(chai, Tea, 'chai is not an instance of tea');
    *
    * @name notInstanceOf
    * @param {Object} object
    * @param {Constructor} constructor
    * @param {String} message
    * @namespace Assert
    * @api public
    */
 
   assert.notInstanceOf = function (val, type, msg) {
     new Assertion(val, msg, assert.notInstanceOf, true)
       .to.not.be.instanceOf(type);
   };
 
   /**
    * ### .include(haystack, needle, [message])
    *
    * Asserts that `haystack` includes `needle`. Can be used to assert the
    * inclusion of a value in an array, a substring in a string, or a subset of
    * properties in an object.
    *
    *     assert.include([1,2,3], 2, 'array contains value');
    *     assert.include('foobar', 'foo', 'string contains substring');
    *     assert.include({ foo: 'bar', hello: 'universe' }, { foo: 'bar' }, 'object contains property');
    *
    * Strict equality (===) is used. When asserting the inclusion of a value in
    * an array, the array is searched for an element that's strictly equal to the
    * given value. When asserting a subset of properties in an object, the object
    * is searched for the given property keys, checking that each one is present
    * and strictly equal to the given property value. For instance:
    *
    *     var obj1 = {a: 1}
    *       , obj2 = {b: 2};
    *     assert.include([obj1, obj2], obj1);
    *     assert.include({foo: obj1, bar: obj2}, {foo: obj1});
    *     assert.include({foo: obj1, bar: obj2}, {foo: obj1, bar: obj2});
    *
    * @name include
    * @param {Array|String} haystack
    * @param {Mixed} needle
    * @param {String} message
    * @namespace Assert
    * @api public
    */
 
   assert.include = function (exp, inc, msg) {
     new Assertion(exp, msg, assert.include, true).include(inc);
   };
 
   /**
    * ### .notInclude(haystack, needle, [message])
    *
    * Asserts that `haystack` does not include `needle`. Can be used to assert
    * the absence of a value in an array, a substring in a string, or a subset of
    * properties in an object.
    *
    *     assert.notInclude([1,2,3], 4, "array doesn't contain value");
    *     assert.notInclude('foobar', 'baz', "string doesn't contain substring");
    *     assert.notInclude({ foo: 'bar', hello: 'universe' }, { foo: 'baz' }, 'object doesn't contain property');
    *
    * Strict equality (===) is used. When asserting the absence of a value in an
    * array, the array is searched to confirm the absence of an element that's
    * strictly equal to the given value. When asserting a subset of properties in
    * an object, the object is searched to confirm that at least one of the given
    * property keys is either not present or not strictly equal to the given
    * property value. For instance:
    *
    *     var obj1 = {a: 1}
    *       , obj2 = {b: 2};
    *     assert.notInclude([obj1, obj2], {a: 1});
    *     assert.notInclude({foo: obj1, bar: obj2}, {foo: {a: 1}});
    *     assert.notInclude({foo: obj1, bar: obj2}, {foo: obj1, bar: {b: 2}});
    *
    * @name notInclude
    * @param {Array|String} haystack
    * @param {Mixed} needle
    * @param {String} message
    * @namespace Assert
    * @api public
    */
 
   assert.notInclude = function (exp, inc, msg) {
     new Assertion(exp, msg, assert.notInclude, true).not.include(inc);
   };
 
   /**
    * ### .deepInclude(haystack, needle, [message])
    *
    * Asserts that `haystack` includes `needle`. Can be used to assert the
    * inclusion of a value in an array or a subset of properties in an object.
    * Deep equality is used.
    *
    *     var obj1 = {a: 1}
    *       , obj2 = {b: 2};
    *     assert.deepInclude([obj1, obj2], {a: 1});
    *     assert.deepInclude({foo: obj1, bar: obj2}, {foo: {a: 1}});
    *     assert.deepInclude({foo: obj1, bar: obj2}, {foo: {a: 1}, bar: {b: 2}});
    *
    * @name deepInclude
    * @param {Array|String} haystack
    * @param {Mixed} needle
    * @param {String} message
    * @namespace Assert
    * @api public
    */
 
   assert.deepInclude = function (exp, inc, msg) {
     new Assertion(exp, msg, assert.deepInclude, true).deep.include(inc);
   };
 
   /**
    * ### .notDeepInclude(haystack, needle, [message])
    *
    * Asserts that `haystack` does not include `needle`. Can be used to assert
    * the absence of a value in an array or a subset of properties in an object.
    * Deep equality is used.
    *
    *     var obj1 = {a: 1}
    *       , obj2 = {b: 2};
    *     assert.notDeepInclude([obj1, obj2], {a: 9});
    *     assert.notDeepInclude({foo: obj1, bar: obj2}, {foo: {a: 9}});
    *     assert.notDeepInclude({foo: obj1, bar: obj2}, {foo: {a: 1}, bar: {b: 9}});
    *
    * @name notDeepInclude
    * @param {Array|String} haystack
    * @param {Mixed} needle
    * @param {String} message
    * @namespace Assert
    * @api public
    */
 
   assert.notDeepInclude = function (exp, inc, msg) {
     new Assertion(exp, msg, assert.notDeepInclude, true).not.deep.include(inc);
   };
 
   /**
    * ### .nestedInclude(haystack, needle, [message])
    *
    * Asserts that 'haystack' includes 'needle'.
    * Can be used to assert the inclusion of a subset of properties in an
    * object.
    * Enables the use of dot- and bracket-notation for referencing nested
    * properties.
    * '[]' and '.' in property names can be escaped using double backslashes.
    *
    *     assert.nestedInclude({'.a': {'b': 'x'}}, {'\\.a.[b]': 'x'});
    *     assert.nestedInclude({'a': {'[b]': 'x'}}, {'a.\\[b\\]': 'x'});
    *
    * @name nestedInclude
    * @param {Object} haystack
    * @param {Object} needle
    * @param {String} message
    * @namespace Assert
    * @api public
    */
 
   assert.nestedInclude = function (exp, inc, msg) {
     new Assertion(exp, msg, assert.nestedInclude, true).nested.include(inc);
   };
 
   /**
    * ### .notNestedInclude(haystack, needle, [message])
    *
    * Asserts that 'haystack' does not include 'needle'.
    * Can be used to assert the absence of a subset of properties in an
    * object.
    * Enables the use of dot- and bracket-notation for referencing nested
    * properties.
    * '[]' and '.' in property names can be escaped using double backslashes.
    *
    *     assert.notNestedInclude({'.a': {'b': 'x'}}, {'\\.a.b': 'y'});
    *     assert.notNestedInclude({'a': {'[b]': 'x'}}, {'a.\\[b\\]': 'y'});
    *
    * @name notNestedInclude
    * @param {Object} haystack
    * @param {Object} needle
    * @param {String} message
    * @namespace Assert
    * @api public
    */
 
   assert.notNestedInclude = function (exp, inc, msg) {
     new Assertion(exp, msg, assert.notNestedInclude, true)
       .not.nested.include(inc);
   };
 
   /**
    * ### .deepNestedInclude(haystack, needle, [message])
    *
    * Asserts that 'haystack' includes 'needle'.
    * Can be used to assert the inclusion of a subset of properties in an
    * object while checking for deep equality.
    * Enables the use of dot- and bracket-notation for referencing nested
    * properties.
    * '[]' and '.' in property names can be escaped using double backslashes.
    *
    *     assert.deepNestedInclude({a: {b: [{x: 1}]}}, {'a.b[0]': {x: 1}});
    *     assert.deepNestedInclude({'.a': {'[b]': {x: 1}}}, {'\\.a.\\[b\\]': {x: 1}});
    *
    * @name deepNestedInclude
    * @param {Object} haystack
    * @param {Object} needle
    * @param {String} message
    * @namespace Assert
    * @api public
    */
 
   assert.deepNestedInclude = function(exp, inc, msg) {
     new Assertion(exp, msg, assert.deepNestedInclude, true)
       .deep.nested.include(inc);
   };
 
   /**
    * ### .notDeepNestedInclude(haystack, needle, [message])
    *
    * Asserts that 'haystack' does not include 'needle'.
    * Can be used to assert the absence of a subset of properties in an
    * object while checking for deep equality.
    * Enables the use of dot- and bracket-notation for referencing nested
    * properties.
    * '[]' and '.' in property names can be escaped using double backslashes.
    *
    *     assert.notDeepNestedInclude({a: {b: [{x: 1}]}}, {'a.b[0]': {y: 1}})
    *     assert.notDeepNestedInclude({'.a': {'[b]': {x: 1}}}, {'\\.a.\\[b\\]': {y: 2}});
    *
    * @name notDeepNestedInclude
    * @param {Object} haystack
    * @param {Object} needle
    * @param {String} message
    * @namespace Assert
    * @api public
    */
 
   assert.notDeepNestedInclude = function(exp, inc, msg) {
     new Assertion(exp, msg, assert.notDeepNestedInclude, true)
       .not.deep.nested.include(inc);
   };
 
   /**
    * ### .ownInclude(haystack, needle, [message])
    *
    * Asserts that 'haystack' includes 'needle'.
    * Can be used to assert the inclusion of a subset of properties in an
    * object while ignoring inherited properties.
    *
    *     assert.ownInclude({ a: 1 }, { a: 1 });
    *
    * @name ownInclude
    * @param {Object} haystack
    * @param {Object} needle
    * @param {String} message
    * @namespace Assert
    * @api public
    */
 
   assert.ownInclude = function(exp, inc, msg) {
     new Assertion(exp, msg, assert.ownInclude, true).own.include(inc);
   };
 
   /**
    * ### .notOwnInclude(haystack, needle, [message])
    *
    * Asserts that 'haystack' includes 'needle'.
    * Can be used to assert the absence of a subset of properties in an
    * object while ignoring inherited properties.
    *
    *     Object.prototype.b = 2;
    *
    *     assert.notOwnInclude({ a: 1 }, { b: 2 });
    *
    * @name notOwnInclude
    * @param {Object} haystack
    * @param {Object} needle
    * @param {String} message
    * @namespace Assert
    * @api public
    */
 
   assert.notOwnInclude = function(exp, inc, msg) {
     new Assertion(exp, msg, assert.notOwnInclude, true).not.own.include(inc);
   };
 
   /**
    * ### .deepOwnInclude(haystack, needle, [message])
    *
    * Asserts that 'haystack' includes 'needle'.
    * Can be used to assert the inclusion of a subset of properties in an
    * object while ignoring inherited properties and checking for deep equality.
    *
    *      assert.deepOwnInclude({a: {b: 2}}, {a: {b: 2}});
    *
    * @name deepOwnInclude
    * @param {Object} haystack
    * @param {Object} needle
    * @param {String} message
    * @namespace Assert
    * @api public
    */
 
   assert.deepOwnInclude = function(exp, inc, msg) {
     new Assertion(exp, msg, assert.deepOwnInclude, true)
       .deep.own.include(inc);
   };
 
    /**
    * ### .notDeepOwnInclude(haystack, needle, [message])
    *
    * Asserts that 'haystack' includes 'needle'.
    * Can be used to assert the absence of a subset of properties in an
    * object while ignoring inherited properties and checking for deep equality.
    *
    *      assert.notDeepOwnInclude({a: {b: 2}}, {a: {c: 3}});
    *
    * @name notDeepOwnInclude
    * @param {Object} haystack
    * @param {Object} needle
    * @param {String} message
    * @namespace Assert
    * @api public
    */
 
   assert.notDeepOwnInclude = function(exp, inc, msg) {
     new Assertion(exp, msg, assert.notDeepOwnInclude, true)
       .not.deep.own.include(inc);
   };
 
   /**
    * ### .match(value, regexp, [message])
    *
    * Asserts that `value` matches the regular expression `regexp`.
    *
    *     assert.match('foobar', /^foo/, 'regexp matches');
    *
    * @name match
    * @param {Mixed} value
    * @param {RegExp} regexp
    * @param {String} message
    * @namespace Assert
    * @api public
    */
 
   assert.match = function (exp, re, msg) {
     new Assertion(exp, msg, assert.match, true).to.match(re);
   };
 
   /**
    * ### .notMatch(value, regexp, [message])
    *
    * Asserts that `value` does not match the regular expression `regexp`.
    *
    *     assert.notMatch('foobar', /^foo/, 'regexp does not match');
    *
    * @name notMatch
    * @param {Mixed} value
    * @param {RegExp} regexp
    * @param {String} message
    * @namespace Assert
    * @api public
    */
 
   assert.notMatch = function (exp, re, msg) {
     new Assertion(exp, msg, assert.notMatch, true).to.not.match(re);
   };
 
   /**
    * ### .property(object, property, [message])
    *
    * Asserts that `object` has a direct or inherited property named by
    * `property`.
    *
    *     assert.property({ tea: { green: 'matcha' }}, 'tea');
    *     assert.property({ tea: { green: 'matcha' }}, 'toString');
    *
    * @name property
    * @param {Object} object
    * @param {String} property
    * @param {String} message
    * @namespace Assert
    * @api public
    */
 
   assert.property = function (obj, prop, msg) {
     new Assertion(obj, msg, assert.property, true).to.have.property(prop);
   };
 
   /**
    * ### .notProperty(object, property, [message])
    *
    * Asserts that `object` does _not_ have a direct or inherited property named
    * by `property`.
    *
    *     assert.notProperty({ tea: { green: 'matcha' }}, 'coffee');
    *
    * @name notProperty
    * @param {Object} object
    * @param {String} property
    * @param {String} message
    * @namespace Assert
    * @api public
    */
 
   assert.notProperty = function (obj, prop, msg) {
     new Assertion(obj, msg, assert.notProperty, true)
       .to.not.have.property(prop);
   };
 
   /**
    * ### .propertyVal(object, property, value, [message])
    *
    * Asserts that `object` has a direct or inherited property named by
    * `property` with a value given by `value`. Uses a strict equality check
    * (===).
    *
    *     assert.propertyVal({ tea: 'is good' }, 'tea', 'is good');
    *
    * @name propertyVal
    * @param {Object} object
    * @param {String} property
    * @param {Mixed} value
    * @param {String} message
    * @namespace Assert
    * @api public
    */
 
   assert.propertyVal = function (obj, prop, val, msg) {
     new Assertion(obj, msg, assert.propertyVal, true)
       .to.have.property(prop, val);
   };
 
   /**
    * ### .notPropertyVal(object, property, value, [message])
    *
    * Asserts that `object` does _not_ have a direct or inherited property named
    * by `property` with value given by `value`. Uses a strict equality check
    * (===).
    *
    *     assert.notPropertyVal({ tea: 'is good' }, 'tea', 'is bad');
    *     assert.notPropertyVal({ tea: 'is good' }, 'coffee', 'is good');
    *
    * @name notPropertyVal
    * @param {Object} object
    * @param {String} property
    * @param {Mixed} value
    * @param {String} message
    * @namespace Assert
    * @api public
    */
 
   assert.notPropertyVal = function (obj, prop, val, msg) {
     new Assertion(obj, msg, assert.notPropertyVal, true)
       .to.not.have.property(prop, val);
   };
 
   /**
    * ### .deepPropertyVal(object, property, value, [message])
    *
    * Asserts that `object` has a direct or inherited property named by
    * `property` with a value given by `value`. Uses a deep equality check.
    *
    *     assert.deepPropertyVal({ tea: { green: 'matcha' } }, 'tea', { green: 'matcha' });
    *
    * @name deepPropertyVal
    * @param {Object} object
    * @param {String} property
    * @param {Mixed} value
    * @param {String} message
    * @namespace Assert
    * @api public
    */
 
   assert.deepPropertyVal = function (obj, prop, val, msg) {
     new Assertion(obj, msg, assert.deepPropertyVal, true)
       .to.have.deep.property(prop, val);
   };
 
   /**
    * ### .notDeepPropertyVal(object, property, value, [message])
    *
    * Asserts that `object` does _not_ have a direct or inherited property named
    * by `property` with value given by `value`. Uses a deep equality check.
    *
    *     assert.notDeepPropertyVal({ tea: { green: 'matcha' } }, 'tea', { black: 'matcha' });
    *     assert.notDeepPropertyVal({ tea: { green: 'matcha' } }, 'tea', { green: 'oolong' });
    *     assert.notDeepPropertyVal({ tea: { green: 'matcha' } }, 'coffee', { green: 'matcha' });
    *
    * @name notDeepPropertyVal
    * @param {Object} object
    * @param {String} property
    * @param {Mixed} value
    * @param {String} message
    * @namespace Assert
    * @api public
    */
 
   assert.notDeepPropertyVal = function (obj, prop, val, msg) {
     new Assertion(obj, msg, assert.notDeepPropertyVal, true)
       .to.not.have.deep.property(prop, val);
   };
 
   /**
    * ### .ownProperty(object, property, [message])
    *
    * Asserts that `object` has a direct property named by `property`. Inherited
    * properties aren't checked.
    *
    *     assert.ownProperty({ tea: { green: 'matcha' }}, 'tea');
    *
    * @name ownProperty
    * @param {Object} object
    * @param {String} property
    * @param {String} message
    * @api public
    */
 
   assert.ownProperty = function (obj, prop, msg) {
     new Assertion(obj, msg, assert.ownProperty, true)
       .to.have.own.property(prop);
   };
 
   /**
    * ### .notOwnProperty(object, property, [message])
    *
    * Asserts that `object` does _not_ have a direct property named by
    * `property`. Inherited properties aren't checked.
    *
    *     assert.notOwnProperty({ tea: { green: 'matcha' }}, 'coffee');
    *     assert.notOwnProperty({}, 'toString');
    *
    * @name notOwnProperty
    * @param {Object} object
    * @param {String} property
    * @param {String} message
    * @api public
    */
 
   assert.notOwnProperty = function (obj, prop, msg) {
     new Assertion(obj, msg, assert.notOwnProperty, true)
       .to.not.have.own.property(prop);
   };
 
   /**
    * ### .ownPropertyVal(object, property, value, [message])
    *
    * Asserts that `object` has a direct property named by `property` and a value
    * equal to the provided `value`. Uses a strict equality check (===).
    * Inherited properties aren't checked.
    *
    *     assert.ownPropertyVal({ coffee: 'is good'}, 'coffee', 'is good');
    *
    * @name ownPropertyVal
    * @param {Object} object
    * @param {String} property
    * @param {Mixed} value
    * @param {String} message
    * @api public
    */
 
   assert.ownPropertyVal = function (obj, prop, value, msg) {
     new Assertion(obj, msg, assert.ownPropertyVal, true)
       .to.have.own.property(prop, value);
   };
 
   /**
    * ### .notOwnPropertyVal(object, property, value, [message])
    *
    * Asserts that `object` does _not_ have a direct property named by `property`
    * with a value equal to the provided `value`. Uses a strict equality check
    * (===). Inherited properties aren't checked.
    *
    *     assert.notOwnPropertyVal({ tea: 'is better'}, 'tea', 'is worse');
    *     assert.notOwnPropertyVal({}, 'toString', Object.prototype.toString);
    *
    * @name notOwnPropertyVal
    * @param {Object} object
    * @param {String} property
    * @param {Mixed} value
    * @param {String} message
    * @api public
    */
 
   assert.notOwnPropertyVal = function (obj, prop, value, msg) {
     new Assertion(obj, msg, assert.notOwnPropertyVal, true)
       .to.not.have.own.property(prop, value);
   };
 
   /**
    * ### .deepOwnPropertyVal(object, property, value, [message])
    *
    * Asserts that `object` has a direct property named by `property` and a value
    * equal to the provided `value`. Uses a deep equality check. Inherited
    * properties aren't checked.
    *
    *     assert.deepOwnPropertyVal({ tea: { green: 'matcha' } }, 'tea', { green: 'matcha' });
    *
    * @name deepOwnPropertyVal
    * @param {Object} object
    * @param {String} property
    * @param {Mixed} value
    * @param {String} message
    * @api public
    */
 
   assert.deepOwnPropertyVal = function (obj, prop, value, msg) {
     new Assertion(obj, msg, assert.deepOwnPropertyVal, true)
       .to.have.deep.own.property(prop, value);
   };
 
   /**
    * ### .notDeepOwnPropertyVal(object, property, value, [message])
    *
    * Asserts that `object` does _not_ have a direct property named by `property`
    * with a value equal to the provided `value`. Uses a deep equality check.
    * Inherited properties aren't checked.
    *
    *     assert.notDeepOwnPropertyVal({ tea: { green: 'matcha' } }, 'tea', { black: 'matcha' });
    *     assert.notDeepOwnPropertyVal({ tea: { green: 'matcha' } }, 'tea', { green: 'oolong' });
    *     assert.notDeepOwnPropertyVal({ tea: { green: 'matcha' } }, 'coffee', { green: 'matcha' });
    *     assert.notDeepOwnPropertyVal({}, 'toString', Object.prototype.toString);
    *
    * @name notDeepOwnPropertyVal
    * @param {Object} object
    * @param {String} property
    * @param {Mixed} value
    * @param {String} message
    * @api public
    */
 
   assert.notDeepOwnPropertyVal = function (obj, prop, value, msg) {
     new Assertion(obj, msg, assert.notDeepOwnPropertyVal, true)
       .to.not.have.deep.own.property(prop, value);
   };
 
   /**
    * ### .nestedProperty(object, property, [message])
    *
    * Asserts that `object` has a direct or inherited property named by
    * `property`, which can be a string using dot- and bracket-notation for
    * nested reference.
    *
    *     assert.nestedProperty({ tea: { green: 'matcha' }}, 'tea.green');
    *
    * @name nestedProperty
    * @param {Object} object
    * @param {String} property
    * @param {String} message
    * @namespace Assert
    * @api public
    */
 
   assert.nestedProperty = function (obj, prop, msg) {
     new Assertion(obj, msg, assert.nestedProperty, true)
       .to.have.nested.property(prop);
   };
 
   /**
    * ### .notNestedProperty(object, property, [message])
    *
    * Asserts that `object` does _not_ have a property named by `property`, which
    * can be a string using dot- and bracket-notation for nested reference. The
    * property cannot exist on the object nor anywhere in its prototype chain.
    *
    *     assert.notNestedProperty({ tea: { green: 'matcha' }}, 'tea.oolong');
    *
    * @name notNestedProperty
    * @param {Object} object
    * @param {String} property
    * @param {String} message
    * @namespace Assert
    * @api public
    */
 
   assert.notNestedProperty = function (obj, prop, msg) {
     new Assertion(obj, msg, assert.notNestedProperty, true)
       .to.not.have.nested.property(prop);
   };
 
   /**
    * ### .nestedPropertyVal(object, property, value, [message])
    *
    * Asserts that `object` has a property named by `property` with value given
    * by `value`. `property` can use dot- and bracket-notation for nested
    * reference. Uses a strict equality check (===).
    *
    *     assert.nestedPropertyVal({ tea: { green: 'matcha' }}, 'tea.green', 'matcha');
    *
    * @name nestedPropertyVal
    * @param {Object} object
    * @param {String} property
    * @param {Mixed} value
    * @param {String} message
    * @namespace Assert
    * @api public
    */
 
   assert.nestedPropertyVal = function (obj, prop, val, msg) {
     new Assertion(obj, msg, assert.nestedPropertyVal, true)
       .to.have.nested.property(prop, val);
   };
 
   /**
    * ### .notNestedPropertyVal(object, property, value, [message])
    *
    * Asserts that `object` does _not_ have a property named by `property` with
    * value given by `value`. `property` can use dot- and bracket-notation for
    * nested reference. Uses a strict equality check (===).
    *
    *     assert.notNestedPropertyVal({ tea: { green: 'matcha' }}, 'tea.green', 'konacha');
    *     assert.notNestedPropertyVal({ tea: { green: 'matcha' }}, 'coffee.green', 'matcha');
    *
    * @name notNestedPropertyVal
    * @param {Object} object
    * @param {String} property
    * @param {Mixed} value
    * @param {String} message
    * @namespace Assert
    * @api public
    */
 
   assert.notNestedPropertyVal = function (obj, prop, val, msg) {
     new Assertion(obj, msg, assert.notNestedPropertyVal, true)
       .to.not.have.nested.property(prop, val);
   };
 
   /**
    * ### .deepNestedPropertyVal(object, property, value, [message])
    *
    * Asserts that `object` has a property named by `property` with a value given
    * by `value`. `property` can use dot- and bracket-notation for nested
    * reference. Uses a deep equality check.
    *
    *     assert.deepNestedPropertyVal({ tea: { green: { matcha: 'yum' } } }, 'tea.green', { matcha: 'yum' });
    *
    * @name deepNestedPropertyVal
    * @param {Object} object
    * @param {String} property
    * @param {Mixed} value
    * @param {String} message
    * @namespace Assert
    * @api public
    */
 
   assert.deepNestedPropertyVal = function (obj, prop, val, msg) {
     new Assertion(obj, msg, assert.deepNestedPropertyVal, true)
       .to.have.deep.nested.property(prop, val);
   };
 
   /**
    * ### .notDeepNestedPropertyVal(object, property, value, [message])
    *
    * Asserts that `object` does _not_ have a property named by `property` with
    * value given by `value`. `property` can use dot- and bracket-notation for
    * nested reference. Uses a deep equality check.
    *
    *     assert.notDeepNestedPropertyVal({ tea: { green: { matcha: 'yum' } } }, 'tea.green', { oolong: 'yum' });
    *     assert.notDeepNestedPropertyVal({ tea: { green: { matcha: 'yum' } } }, 'tea.green', { matcha: 'yuck' });
    *     assert.notDeepNestedPropertyVal({ tea: { green: { matcha: 'yum' } } }, 'tea.black', { matcha: 'yum' });
    *
    * @name notDeepNestedPropertyVal
    * @param {Object} object
    * @param {String} property
    * @param {Mixed} value
    * @param {String} message
    * @namespace Assert
    * @api public
    */
 
   assert.notDeepNestedPropertyVal = function (obj, prop, val, msg) {
     new Assertion(obj, msg, assert.notDeepNestedPropertyVal, true)
       .to.not.have.deep.nested.property(prop, val);
   }
 
   /**
    * ### .lengthOf(object, length, [message])
    *
    * Asserts that `object` has a `length` or `size` with the expected value.
    *
    *     assert.lengthOf([1,2,3], 3, 'array has length of 3');
    *     assert.lengthOf('foobar', 6, 'string has length of 6');
    *     assert.lengthOf(new Set([1,2,3]), 3, 'set has size of 3');
    *     assert.lengthOf(new Map([['a',1],['b',2],['c',3]]), 3, 'map has size of 3');
    *
    * @name lengthOf
    * @param {Mixed} object
    * @param {Number} length
    * @param {String} message
    * @namespace Assert
    * @api public
    */
 
   assert.lengthOf = function (exp, len, msg) {
     new Assertion(exp, msg, assert.lengthOf, true).to.have.lengthOf(len);
   };
 
   /**
    * ### .hasAnyKeys(object, [keys], [message])
    *
    * Asserts that `object` has at least one of the `keys` provided.
    * You can also provide a single object instead of a `keys` array and its keys
    * will be used as the expected set of keys.
    *
    *     assert.hasAnyKeys({foo: 1, bar: 2, baz: 3}, ['foo', 'iDontExist', 'baz']);
    *     assert.hasAnyKeys({foo: 1, bar: 2, baz: 3}, {foo: 30, iDontExist: 99, baz: 1337});
    *     assert.hasAnyKeys(new Map([[{foo: 1}, 'bar'], ['key', 'value']]), [{foo: 1}, 'key']);
    *     assert.hasAnyKeys(new Set([{foo: 'bar'}, 'anotherKey']), [{foo: 'bar'}, 'anotherKey']);
    *
    * @name hasAnyKeys
    * @param {Mixed} object
    * @param {Array|Object} keys
    * @param {String} message
    * @namespace Assert
    * @api public
    */
 
   assert.hasAnyKeys = function (obj, keys, msg) {
     new Assertion(obj, msg, assert.hasAnyKeys, true).to.have.any.keys(keys);
   }
 
   /**
    * ### .hasAllKeys(object, [keys], [message])
    *
    * Asserts that `object` has all and only all of the `keys` provided.
    * You can also provide a single object instead of a `keys` array and its keys
    * will be used as the expected set of keys.
    *
    *     assert.hasAllKeys({foo: 1, bar: 2, baz: 3}, ['foo', 'bar', 'baz']);
    *     assert.hasAllKeys({foo: 1, bar: 2, baz: 3}, {foo: 30, bar: 99, baz: 1337]);
    *     assert.hasAllKeys(new Map([[{foo: 1}, 'bar'], ['key', 'value']]), [{foo: 1}, 'key']);
    *     assert.hasAllKeys(new Set([{foo: 'bar'}, 'anotherKey'], [{foo: 'bar'}, 'anotherKey']);
    *
    * @name hasAllKeys
    * @param {Mixed} object
    * @param {String[]} keys
    * @param {String} message
    * @namespace Assert
    * @api public
    */
 
   assert.hasAllKeys = function (obj, keys, msg) {
     new Assertion(obj, msg, assert.hasAllKeys, true).to.have.all.keys(keys);
   }
 
   /**
    * ### .containsAllKeys(object, [keys], [message])
    *
    * Asserts that `object` has all of the `keys` provided but may have more keys not listed.
    * You can also provide a single object instead of a `keys` array and its keys
    * will be used as the expected set of keys.
    *
    *     assert.containsAllKeys({foo: 1, bar: 2, baz: 3}, ['foo', 'baz']);
    *     assert.containsAllKeys({foo: 1, bar: 2, baz: 3}, ['foo', 'bar', 'baz']);
    *     assert.containsAllKeys({foo: 1, bar: 2, baz: 3}, {foo: 30, baz: 1337});
    *     assert.containsAllKeys({foo: 1, bar: 2, baz: 3}, {foo: 30, bar: 99, baz: 1337});
    *     assert.containsAllKeys(new Map([[{foo: 1}, 'bar'], ['key', 'value']]), [{foo: 1}]);
    *     assert.containsAllKeys(new Map([[{foo: 1}, 'bar'], ['key', 'value']]), [{foo: 1}, 'key']);
    *     assert.containsAllKeys(new Set([{foo: 'bar'}, 'anotherKey'], [{foo: 'bar'}]);
    *     assert.containsAllKeys(new Set([{foo: 'bar'}, 'anotherKey'], [{foo: 'bar'}, 'anotherKey']);
    *
    * @name containsAllKeys
    * @param {Mixed} object
    * @param {String[]} keys
    * @param {String} message
    * @namespace Assert
    * @api public
    */
 
   assert.containsAllKeys = function (obj, keys, msg) {
     new Assertion(obj, msg, assert.containsAllKeys, true)
       .to.contain.all.keys(keys);
   }
 
   /**
    * ### .doesNotHaveAnyKeys(object, [keys], [message])
    *
    * Asserts that `object` has none of the `keys` provided.
    * You can also provide a single object instead of a `keys` array and its keys
    * will be used as the expected set of keys.
    *
    *     assert.doesNotHaveAnyKeys({foo: 1, bar: 2, baz: 3}, ['one', 'two', 'example']);
    *     assert.doesNotHaveAnyKeys({foo: 1, bar: 2, baz: 3}, {one: 1, two: 2, example: 'foo'});
    *     assert.doesNotHaveAnyKeys(new Map([[{foo: 1}, 'bar'], ['key', 'value']]), [{one: 'two'}, 'example']);
    *     assert.doesNotHaveAnyKeys(new Set([{foo: 'bar'}, 'anotherKey'], [{one: 'two'}, 'example']);
    *
    * @name doesNotHaveAnyKeys
    * @param {Mixed} object
    * @param {String[]} keys
    * @param {String} message
    * @namespace Assert
    * @api public
    */
 
   assert.doesNotHaveAnyKeys = function (obj, keys, msg) {
     new Assertion(obj, msg, assert.doesNotHaveAnyKeys, true)
       .to.not.have.any.keys(keys);
   }
 
   /**
    * ### .doesNotHaveAllKeys(object, [keys], [message])
    *
    * Asserts that `object` does not have at least one of the `keys` provided.
    * You can also provide a single object instead of a `keys` array and its keys
    * will be used as the expected set of keys.
    *
    *     assert.doesNotHaveAllKeys({foo: 1, bar: 2, baz: 3}, ['one', 'two', 'example']);
    *     assert.doesNotHaveAllKeys({foo: 1, bar: 2, baz: 3}, {one: 1, two: 2, example: 'foo'});
    *     assert.doesNotHaveAllKeys(new Map([[{foo: 1}, 'bar'], ['key', 'value']]), [{one: 'two'}, 'example']);
    *     assert.doesNotHaveAllKeys(new Set([{foo: 'bar'}, 'anotherKey'], [{one: 'two'}, 'example']);
    *
    * @name doesNotHaveAllKeys
    * @param {Mixed} object
    * @param {String[]} keys
    * @param {String} message
    * @namespace Assert
    * @api public
    */
 
   assert.doesNotHaveAllKeys = function (obj, keys, msg) {
     new Assertion(obj, msg, assert.doesNotHaveAllKeys, true)
       .to.not.have.all.keys(keys);
   }
 
   /**
    * ### .hasAnyDeepKeys(object, [keys], [message])
    *
    * Asserts that `object` has at least one of the `keys` provided.
    * Since Sets and Maps can have objects as keys you can use this assertion to perform
    * a deep comparison.
    * You can also provide a single object instead of a `keys` array and its keys
    * will be used as the expected set of keys.
    *
    *     assert.hasAnyDeepKeys(new Map([[{one: 'one'}, 'valueOne'], [1, 2]]), {one: 'one'});
    *     assert.hasAnyDeepKeys(new Map([[{one: 'one'}, 'valueOne'], [1, 2]]), [{one: 'one'}, {two: 'two'}]);
    *     assert.hasAnyDeepKeys(new Map([[{one: 'one'}, 'valueOne'], [{two: 'two'}, 'valueTwo']]), [{one: 'one'}, {two: 'two'}]);
    *     assert.hasAnyDeepKeys(new Set([{one: 'one'}, {two: 'two'}]), {one: 'one'});
    *     assert.hasAnyDeepKeys(new Set([{one: 'one'}, {two: 'two'}]), [{one: 'one'}, {three: 'three'}]);
    *     assert.hasAnyDeepKeys(new Set([{one: 'one'}, {two: 'two'}]), [{one: 'one'}, {two: 'two'}]);
    *
    * @name hasAnyDeepKeys
    * @param {Mixed} object
    * @param {Array|Object} keys
    * @param {String} message
    * @namespace Assert
    * @api public
    */
 
   assert.hasAnyDeepKeys = function (obj, keys, msg) {
     new Assertion(obj, msg, assert.hasAnyDeepKeys, true)
       .to.have.any.deep.keys(keys);
   }
 
  /**
    * ### .hasAllDeepKeys(object, [keys], [message])
    *
    * Asserts that `object` has all and only all of the `keys` provided.
    * Since Sets and Maps can have objects as keys you can use this assertion to perform
    * a deep comparison.
    * You can also provide a single object instead of a `keys` array and its keys
    * will be used as the expected set of keys.
    *
    *     assert.hasAllDeepKeys(new Map([[{one: 'one'}, 'valueOne']]), {one: 'one'});
    *     assert.hasAllDeepKeys(new Map([[{one: 'one'}, 'valueOne'], [{two: 'two'}, 'valueTwo']]), [{one: 'one'}, {two: 'two'}]);
    *     assert.hasAllDeepKeys(new Set([{one: 'one'}]), {one: 'one'});
    *     assert.hasAllDeepKeys(new Set([{one: 'one'}, {two: 'two'}]), [{one: 'one'}, {two: 'two'}]);
    *
    * @name hasAllDeepKeys
    * @param {Mixed} object
    * @param {Array|Object} keys
    * @param {String} message
    * @namespace Assert
    * @api public
    */
 
   assert.hasAllDeepKeys = function (obj, keys, msg) {
     new Assertion(obj, msg, assert.hasAllDeepKeys, true)
       .to.have.all.deep.keys(keys);
   }
 
  /**
    * ### .containsAllDeepKeys(object, [keys], [message])
    *
    * Asserts that `object` contains all of the `keys` provided.
    * Since Sets and Maps can have objects as keys you can use this assertion to perform
    * a deep comparison.
    * You can also provide a single object instead of a `keys` array and its keys
    * will be used as the expected set of keys.
    *
    *     assert.containsAllDeepKeys(new Map([[{one: 'one'}, 'valueOne'], [1, 2]]), {one: 'one'});
    *     assert.containsAllDeepKeys(new Map([[{one: 'one'}, 'valueOne'], [{two: 'two'}, 'valueTwo']]), [{one: 'one'}, {two: 'two'}]);
    *     assert.containsAllDeepKeys(new Set([{one: 'one'}, {two: 'two'}]), {one: 'one'});
    *     assert.containsAllDeepKeys(new Set([{one: 'one'}, {two: 'two'}]), [{one: 'one'}, {two: 'two'}]);
    *
    * @name containsAllDeepKeys
    * @param {Mixed} object
    * @param {Array|Object} keys
    * @param {String} message
    * @namespace Assert
    * @api public
    */
 
   assert.containsAllDeepKeys = function (obj, keys, msg) {
     new Assertion(obj, msg, assert.containsAllDeepKeys, true)
       .to.contain.all.deep.keys(keys);
   }
 
  /**
    * ### .doesNotHaveAnyDeepKeys(object, [keys], [message])
    *
    * Asserts that `object` has none of the `keys` provided.
    * Since Sets and Maps can have objects as keys you can use this assertion to perform
    * a deep comparison.
    * You can also provide a single object instead of a `keys` array and its keys
    * will be used as the expected set of keys.
    *
    *     assert.doesNotHaveAnyDeepKeys(new Map([[{one: 'one'}, 'valueOne'], [1, 2]]), {thisDoesNot: 'exist'});
    *     assert.doesNotHaveAnyDeepKeys(new Map([[{one: 'one'}, 'valueOne'], [{two: 'two'}, 'valueTwo']]), [{twenty: 'twenty'}, {fifty: 'fifty'}]);
    *     assert.doesNotHaveAnyDeepKeys(new Set([{one: 'one'}, {two: 'two'}]), {twenty: 'twenty'});
    *     assert.doesNotHaveAnyDeepKeys(new Set([{one: 'one'}, {two: 'two'}]), [{twenty: 'twenty'}, {fifty: 'fifty'}]);
    *
    * @name doesNotHaveAnyDeepKeys
    * @param {Mixed} object
    * @param {Array|Object} keys
    * @param {String} message
    * @namespace Assert
    * @api public
    */
 
   assert.doesNotHaveAnyDeepKeys = function (obj, keys, msg) {
     new Assertion(obj, msg, assert.doesNotHaveAnyDeepKeys, true)
       .to.not.have.any.deep.keys(keys);
   }
 
  /**
    * ### .doesNotHaveAllDeepKeys(object, [keys], [message])
    *
    * Asserts that `object` does not have at least one of the `keys` provided.
    * Since Sets and Maps can have objects as keys you can use this assertion to perform
    * a deep comparison.
    * You can also provide a single object instead of a `keys` array and its keys
    * will be used as the expected set of keys.
    *
    *     assert.doesNotHaveAllDeepKeys(new Map([[{one: 'one'}, 'valueOne'], [1, 2]]), {thisDoesNot: 'exist'});
    *     assert.doesNotHaveAllDeepKeys(new Map([[{one: 'one'}, 'valueOne'], [{two: 'two'}, 'valueTwo']]), [{twenty: 'twenty'}, {one: 'one'}]);
    *     assert.doesNotHaveAllDeepKeys(new Set([{one: 'one'}, {two: 'two'}]), {twenty: 'twenty'});
    *     assert.doesNotHaveAllDeepKeys(new Set([{one: 'one'}, {two: 'two'}]), [{one: 'one'}, {fifty: 'fifty'}]);
    *
    * @name doesNotHaveAllDeepKeys
    * @param {Mixed} object
    * @param {Array|Object} keys
    * @param {String} message
    * @namespace Assert
    * @api public
    */
 
   assert.doesNotHaveAllDeepKeys = function (obj, keys, msg) {
     new Assertion(obj, msg, assert.doesNotHaveAllDeepKeys, true)
       .to.not.have.all.deep.keys(keys);
   }
 
  /**
    * ### .throws(fn, [errorLike/string/regexp], [string/regexp], [message])
    *
    * If `errorLike` is an `Error` constructor, asserts that `fn` will throw an error that is an
    * instance of `errorLike`.
    * If `errorLike` is an `Error` instance, asserts that the error thrown is the same
    * instance as `errorLike`.
    * If `errMsgMatcher` is provided, it also asserts that the error thrown will have a
    * message matching `errMsgMatcher`.
    *
    *     assert.throws(fn, 'Error thrown must have this msg');
    *     assert.throws(fn, /Error thrown must have a msg that matches this/);
    *     assert.throws(fn, ReferenceError);
    *     assert.throws(fn, errorInstance);
    *     assert.throws(fn, ReferenceError, 'Error thrown must be a ReferenceError and have this msg');
    *     assert.throws(fn, errorInstance, 'Error thrown must be the same errorInstance and have this msg');
    *     assert.throws(fn, ReferenceError, /Error thrown must be a ReferenceError and match this/);
    *     assert.throws(fn, errorInstance, /Error thrown must be the same errorInstance and match this/);
    *
    * @name throws
    * @alias throw
    * @alias Throw
    * @param {Function} fn
    * @param {ErrorConstructor|Error} errorLike
    * @param {RegExp|String} errMsgMatcher
    * @param {String} message
    * @see https://developer.mozilla.org/en/JavaScript/Reference/Global_Objects/Error#Error_types
    * @namespace Assert
    * @api public
    */
 
   assert.throws = function (fn, errorLike, errMsgMatcher, msg) {
     if ('string' === typeof errorLike || errorLike instanceof RegExp) {
       errMsgMatcher = errorLike;
       errorLike = null;
     }
 
     var assertErr = new Assertion(fn, msg, assert.throws, true)
       .to.throw(errorLike, errMsgMatcher);
     return flag(assertErr, 'object');
   };
 
   /**
    * ### .doesNotThrow(fn, [errorLike/string/regexp], [string/regexp], [message])
    *
    * If `errorLike` is an `Error` constructor, asserts that `fn` will _not_ throw an error that is an
    * instance of `errorLike`.
    * If `errorLike` is an `Error` instance, asserts that the error thrown is _not_ the same
    * instance as `errorLike`.
    * If `errMsgMatcher` is provided, it also asserts that the error thrown will _not_ have a
    * message matching `errMsgMatcher`.
    *
    *     assert.doesNotThrow(fn, 'Any Error thrown must not have this message');
    *     assert.doesNotThrow(fn, /Any Error thrown must not match this/);
    *     assert.doesNotThrow(fn, Error);
    *     assert.doesNotThrow(fn, errorInstance);
    *     assert.doesNotThrow(fn, Error, 'Error must not have this message');
    *     assert.doesNotThrow(fn, errorInstance, 'Error must not have this message');
    *     assert.doesNotThrow(fn, Error, /Error must not match this/);
    *     assert.doesNotThrow(fn, errorInstance, /Error must not match this/);
    *
    * @name doesNotThrow
    * @param {Function} fn
    * @param {ErrorConstructor} errorLike
    * @param {RegExp|String} errMsgMatcher
    * @param {String} message
    * @see https://developer.mozilla.org/en/JavaScript/Reference/Global_Objects/Error#Error_types
    * @namespace Assert
    * @api public
    */
 
   assert.doesNotThrow = function (fn, errorLike, errMsgMatcher, msg) {
     if ('string' === typeof errorLike || errorLike instanceof RegExp) {
       errMsgMatcher = errorLike;
       errorLike = null;
     }
 
     new Assertion(fn, msg, assert.doesNotThrow, true)
       .to.not.throw(errorLike, errMsgMatcher);
   };
 
   /**
    * ### .operator(val1, operator, val2, [message])
    *
    * Compares two values using `operator`.
    *
    *     assert.operator(1, '<', 2, 'everything is ok');
    *     assert.operator(1, '>', 2, 'this will fail');
    *
    * @name operator
    * @param {Mixed} val1
    * @param {String} operator
    * @param {Mixed} val2
    * @param {String} message
    * @namespace Assert
    * @api public
    */
 
   assert.operator = function (val, operator, val2, msg) {
     var ok;
     switch(operator) {
       case '==':
         ok = val == val2;
         break;
       case '===':
         ok = val === val2;
         break;
       case '>':
         ok = val > val2;
         break;
       case '>=':
         ok = val >= val2;
         break;
       case '<':
         ok = val < val2;
         break;
       case '<=':
         ok = val <= val2;
         break;
       case '!=':
         ok = val != val2;
         break;
       case '!==':
         ok = val !== val2;
         break;
       default:
         msg = msg ? msg + ': ' : msg;
         throw new chai.AssertionError(
           msg + 'Invalid operator "' + operator + '"',
           undefined,
           assert.operator
         );
     }
     var test = new Assertion(ok, msg, assert.operator, true);
     test.assert(
         true === flag(test, 'object')
       , 'expected ' + util.inspect(val) + ' to be ' + operator + ' ' + util.inspect(val2)
       , 'expected ' + util.inspect(val) + ' to not be ' + operator + ' ' + util.inspect(val2) );
   };
 
   /**
    * ### .closeTo(actual, expected, delta, [message])
    *
    * Asserts that the target is equal `expected`, to within a +/- `delta` range.
    *
    *     assert.closeTo(1.5, 1, 0.5, 'numbers are close');
    *
    * @name closeTo
    * @param {Number} actual
    * @param {Number} expected
    * @param {Number} delta
    * @param {String} message
    * @namespace Assert
    * @api public
    */
 
   assert.closeTo = function (act, exp, delta, msg) {
     new Assertion(act, msg, assert.closeTo, true).to.be.closeTo(exp, delta);
   };
 
   /**
    * ### .approximately(actual, expected, delta, [message])
    *
    * Asserts that the target is equal `expected`, to within a +/- `delta` range.
    *
    *     assert.approximately(1.5, 1, 0.5, 'numbers are close');
    *
    * @name approximately
    * @param {Number} actual
    * @param {Number} expected
    * @param {Number} delta
    * @param {String} message
    * @namespace Assert
    * @api public
    */
 
   assert.approximately = function (act, exp, delta, msg) {
     new Assertion(act, msg, assert.approximately, true)
       .to.be.approximately(exp, delta);
   };
 
   /**
    * ### .sameMembers(set1, set2, [message])
    *
    * Asserts that `set1` and `set2` have the same members in any order. Uses a
    * strict equality check (===).
    *
    *     assert.sameMembers([ 1, 2, 3 ], [ 2, 1, 3 ], 'same members');
    *
    * @name sameMembers
    * @param {Array} set1
    * @param {Array} set2
    * @param {String} message
    * @namespace Assert
    * @api public
    */
 
   assert.sameMembers = function (set1, set2, msg) {
     new Assertion(set1, msg, assert.sameMembers, true)
       .to.have.same.members(set2);
   }
 
   /**
    * ### .notSameMembers(set1, set2, [message])
    *
    * Asserts that `set1` and `set2` don't have the same members in any order.
    * Uses a strict equality check (===).
    *
    *     assert.notSameMembers([ 1, 2, 3 ], [ 5, 1, 3 ], 'not same members');
    *
    * @name notSameMembers
    * @param {Array} set1
    * @param {Array} set2
    * @param {String} message
    * @namespace Assert
    * @api public
    */
 
   assert.notSameMembers = function (set1, set2, msg) {
     new Assertion(set1, msg, assert.notSameMembers, true)
       .to.not.have.same.members(set2);
   }
 
   /**
    * ### .sameDeepMembers(set1, set2, [message])
    *
    * Asserts that `set1` and `set2` have the same members in any order. Uses a
    * deep equality check.
    *
    *     assert.sameDeepMembers([ { a: 1 }, { b: 2 }, { c: 3 } ], [{ b: 2 }, { a: 1 }, { c: 3 }], 'same deep members');
    *
    * @name sameDeepMembers
    * @param {Array} set1
    * @param {Array} set2
    * @param {String} message
    * @namespace Assert
    * @api public
    */
 
   assert.sameDeepMembers = function (set1, set2, msg) {
     new Assertion(set1, msg, assert.sameDeepMembers, true)
       .to.have.same.deep.members(set2);
   }
 
   /**
    * ### .notSameDeepMembers(set1, set2, [message])
    *
    * Asserts that `set1` and `set2` don't have the same members in any order.
    * Uses a deep equality check.
    *
    *     assert.notSameDeepMembers([ { a: 1 }, { b: 2 }, { c: 3 } ], [{ b: 2 }, { a: 1 }, { f: 5 }], 'not same deep members');
    *
    * @name notSameDeepMembers
    * @param {Array} set1
    * @param {Array} set2
    * @param {String} message
    * @namespace Assert
    * @api public
    */
 
   assert.notSameDeepMembers = function (set1, set2, msg) {
     new Assertion(set1, msg, assert.notSameDeepMembers, true)
       .to.not.have.same.deep.members(set2);
   }
 
   /**
    * ### .sameOrderedMembers(set1, set2, [message])
    *
    * Asserts that `set1` and `set2` have the same members in the same order.
    * Uses a strict equality check (===).
    *
    *     assert.sameOrderedMembers([ 1, 2, 3 ], [ 1, 2, 3 ], 'same ordered members');
    *
    * @name sameOrderedMembers
    * @param {Array} set1
    * @param {Array} set2
    * @param {String} message
    * @namespace Assert
    * @api public
    */
 
   assert.sameOrderedMembers = function (set1, set2, msg) {
     new Assertion(set1, msg, assert.sameOrderedMembers, true)
       .to.have.same.ordered.members(set2);
   }
 
   /**
    * ### .notSameOrderedMembers(set1, set2, [message])
    *
    * Asserts that `set1` and `set2` don't have the same members in the same
    * order. Uses a strict equality check (===).
    *
    *     assert.notSameOrderedMembers([ 1, 2, 3 ], [ 2, 1, 3 ], 'not same ordered members');
    *
    * @name notSameOrderedMembers
    * @param {Array} set1
    * @param {Array} set2
    * @param {String} message
    * @namespace Assert
    * @api public
    */
 
   assert.notSameOrderedMembers = function (set1, set2, msg) {
     new Assertion(set1, msg, assert.notSameOrderedMembers, true)
       .to.not.have.same.ordered.members(set2);
   }
 
   /**
    * ### .sameDeepOrderedMembers(set1, set2, [message])
    *
    * Asserts that `set1` and `set2` have the same members in the same order.
    * Uses a deep equality check.
    *
    *     assert.sameDeepOrderedMembers([ { a: 1 }, { b: 2 }, { c: 3 } ], [ { a: 1 }, { b: 2 }, { c: 3 } ], 'same deep ordered members');
    *
    * @name sameDeepOrderedMembers
    * @param {Array} set1
    * @param {Array} set2
    * @param {String} message
    * @namespace Assert
    * @api public
    */
 
   assert.sameDeepOrderedMembers = function (set1, set2, msg) {
     new Assertion(set1, msg, assert.sameDeepOrderedMembers, true)
       .to.have.same.deep.ordered.members(set2);
   }
 
   /**
    * ### .notSameDeepOrderedMembers(set1, set2, [message])
    *
    * Asserts that `set1` and `set2` don't have the same members in the same
    * order. Uses a deep equality check.
    *
    *     assert.notSameDeepOrderedMembers([ { a: 1 }, { b: 2 }, { c: 3 } ], [ { a: 1 }, { b: 2 }, { z: 5 } ], 'not same deep ordered members');
    *     assert.notSameDeepOrderedMembers([ { a: 1 }, { b: 2 }, { c: 3 } ], [ { b: 2 }, { a: 1 }, { c: 3 } ], 'not same deep ordered members');
    *
    * @name notSameDeepOrderedMembers
    * @param {Array} set1
    * @param {Array} set2
    * @param {String} message
    * @namespace Assert
    * @api public
    */
 
   assert.notSameDeepOrderedMembers = function (set1, set2, msg) {
     new Assertion(set1, msg, assert.notSameDeepOrderedMembers, true)
       .to.not.have.same.deep.ordered.members(set2);
   }
 
   /**
    * ### .includeMembers(superset, subset, [message])
    *
    * Asserts that `subset` is included in `superset` in any order. Uses a
    * strict equality check (===). Duplicates are ignored.
    *
    *     assert.includeMembers([ 1, 2, 3 ], [ 2, 1, 2 ], 'include members');
    *
    * @name includeMembers
    * @param {Array} superset
    * @param {Array} subset
    * @param {String} message
    * @namespace Assert
    * @api public
    */
 
   assert.includeMembers = function (superset, subset, msg) {
     new Assertion(superset, msg, assert.includeMembers, true)
       .to.include.members(subset);
   }
 
   /**
    * ### .notIncludeMembers(superset, subset, [message])
    *
    * Asserts that `subset` isn't included in `superset` in any order. Uses a
    * strict equality check (===). Duplicates are ignored.
    *
    *     assert.notIncludeMembers([ 1, 2, 3 ], [ 5, 1 ], 'not include members');
    *
    * @name notIncludeMembers
    * @param {Array} superset
    * @param {Array} subset
    * @param {String} message
    * @namespace Assert
    * @api public
    */
 
   assert.notIncludeMembers = function (superset, subset, msg) {
     new Assertion(superset, msg, assert.notIncludeMembers, true)
       .to.not.include.members(subset);
   }
 
   /**
    * ### .includeDeepMembers(superset, subset, [message])
    *
    * Asserts that `subset` is included in `superset` in any order. Uses a deep
    * equality check. Duplicates are ignored.
    *
    *     assert.includeDeepMembers([ { a: 1 }, { b: 2 }, { c: 3 } ], [ { b: 2 }, { a: 1 }, { b: 2 } ], 'include deep members');
    *
    * @name includeDeepMembers
    * @param {Array} superset
    * @param {Array} subset
    * @param {String} message
    * @namespace Assert
    * @api public
    */
 
   assert.includeDeepMembers = function (superset, subset, msg) {
     new Assertion(superset, msg, assert.includeDeepMembers, true)
       .to.include.deep.members(subset);
   }
 
   /**
    * ### .notIncludeDeepMembers(superset, subset, [message])
    *
    * Asserts that `subset` isn't included in `superset` in any order. Uses a
    * deep equality check. Duplicates are ignored.
    *
    *     assert.notIncludeDeepMembers([ { a: 1 }, { b: 2 }, { c: 3 } ], [ { b: 2 }, { f: 5 } ], 'not include deep members');
    *
    * @name notIncludeDeepMembers
    * @param {Array} superset
    * @param {Array} subset
    * @param {String} message
    * @namespace Assert
    * @api public
    */
 
   assert.notIncludeDeepMembers = function (superset, subset, msg) {
     new Assertion(superset, msg, assert.notIncludeDeepMembers, true)
       .to.not.include.deep.members(subset);
   }
 
   /**
    * ### .includeOrderedMembers(superset, subset, [message])
    *
    * Asserts that `subset` is included in `superset` in the same order
    * beginning with the first element in `superset`. Uses a strict equality
    * check (===).
    *
    *     assert.includeOrderedMembers([ 1, 2, 3 ], [ 1, 2 ], 'include ordered members');
    *
    * @name includeOrderedMembers
    * @param {Array} superset
    * @param {Array} subset
    * @param {String} message
    * @namespace Assert
    * @api public
    */
 
   assert.includeOrderedMembers = function (superset, subset, msg) {
     new Assertion(superset, msg, assert.includeOrderedMembers, true)
       .to.include.ordered.members(subset);
   }
 
   /**
    * ### .notIncludeOrderedMembers(superset, subset, [message])
    *
    * Asserts that `subset` isn't included in `superset` in the same order
    * beginning with the first element in `superset`. Uses a strict equality
    * check (===).
    *
    *     assert.notIncludeOrderedMembers([ 1, 2, 3 ], [ 2, 1 ], 'not include ordered members');
    *     assert.notIncludeOrderedMembers([ 1, 2, 3 ], [ 2, 3 ], 'not include ordered members');
    *
    * @name notIncludeOrderedMembers
    * @param {Array} superset
    * @param {Array} subset
    * @param {String} message
    * @namespace Assert
    * @api public
    */
 
   assert.notIncludeOrderedMembers = function (superset, subset, msg) {
     new Assertion(superset, msg, assert.notIncludeOrderedMembers, true)
       .to.not.include.ordered.members(subset);
   }
 
   /**
    * ### .includeDeepOrderedMembers(superset, subset, [message])
    *
    * Asserts that `subset` is included in `superset` in the same order
    * beginning with the first element in `superset`. Uses a deep equality
    * check.
    *
    *     assert.includeDeepOrderedMembers([ { a: 1 }, { b: 2 }, { c: 3 } ], [ { a: 1 }, { b: 2 } ], 'include deep ordered members');
    *
    * @name includeDeepOrderedMembers
    * @param {Array} superset
    * @param {Array} subset
    * @param {String} message
    * @namespace Assert
    * @api public
    */
 
   assert.includeDeepOrderedMembers = function (superset, subset, msg) {
     new Assertion(superset, msg, assert.includeDeepOrderedMembers, true)
       .to.include.deep.ordered.members(subset);
   }
 
   /**
    * ### .notIncludeDeepOrderedMembers(superset, subset, [message])
    *
    * Asserts that `subset` isn't included in `superset` in the same order
    * beginning with the first element in `superset`. Uses a deep equality
    * check.
    *
    *     assert.notIncludeDeepOrderedMembers([ { a: 1 }, { b: 2 }, { c: 3 } ], [ { a: 1 }, { f: 5 } ], 'not include deep ordered members');
    *     assert.notIncludeDeepOrderedMembers([ { a: 1 }, { b: 2 }, { c: 3 } ], [ { b: 2 }, { a: 1 } ], 'not include deep ordered members');
    *     assert.notIncludeDeepOrderedMembers([ { a: 1 }, { b: 2 }, { c: 3 } ], [ { b: 2 }, { c: 3 } ], 'not include deep ordered members');
    *
    * @name notIncludeDeepOrderedMembers
    * @param {Array} superset
    * @param {Array} subset
    * @param {String} message
    * @namespace Assert
    * @api public
    */
 
   assert.notIncludeDeepOrderedMembers = function (superset, subset, msg) {
     new Assertion(superset, msg, assert.notIncludeDeepOrderedMembers, true)
       .to.not.include.deep.ordered.members(subset);
   }
 
   /**
    * ### .oneOf(inList, list, [message])
    *
    * Asserts that non-object, non-array value `inList` appears in the flat array `list`.
    *
    *     assert.oneOf(1, [ 2, 1 ], 'Not found in list');
    *
    * @name oneOf
    * @param {*} inList
    * @param {Array<*>} list
    * @param {String} message
    * @namespace Assert
    * @api public
    */
 
   assert.oneOf = function (inList, list, msg) {
     new Assertion(inList, msg, assert.oneOf, true).to.be.oneOf(list);
   }
 
   /**
    * ### .changes(function, object, property, [message])
    *
    * Asserts that a function changes the value of a property.
    *
    *     var obj = { val: 10 };
    *     var fn = function() { obj.val = 22 };
    *     assert.changes(fn, obj, 'val');
    *
    * @name changes
    * @param {Function} modifier function
    * @param {Object} object or getter function
    * @param {String} property name _optional_
    * @param {String} message _optional_
    * @namespace Assert
    * @api public
    */
 
   assert.changes = function (fn, obj, prop, msg) {
     if (arguments.length === 3 && typeof obj === 'function') {
       msg = prop;
       prop = null;
     }
 
     new Assertion(fn, msg, assert.changes, true).to.change(obj, prop);
   }
 
    /**
    * ### .changesBy(function, object, property, delta, [message])
    *
    * Asserts that a function changes the value of a property by an amount (delta).
    *
    *     var obj = { val: 10 };
    *     var fn = function() { obj.val += 2 };
    *     assert.changesBy(fn, obj, 'val', 2);
    *
    * @name changesBy
    * @param {Function} modifier function
    * @param {Object} object or getter function
    * @param {String} property name _optional_
    * @param {Number} change amount (delta)
    * @param {String} message _optional_
    * @namespace Assert
    * @api public
    */
 
   assert.changesBy = function (fn, obj, prop, delta, msg) {
     if (arguments.length === 4 && typeof obj === 'function') {
       var tmpMsg = delta;
       delta = prop;
       msg = tmpMsg;
     } else if (arguments.length === 3) {
       delta = prop;
       prop = null;
     }
 
     new Assertion(fn, msg, assert.changesBy, true)
       .to.change(obj, prop).by(delta);
   }
 
    /**
    * ### .doesNotChange(function, object, property, [message])
    *
    * Asserts that a function does not change the value of a property.
    *
    *     var obj = { val: 10 };
    *     var fn = function() { console.log('foo'); };
    *     assert.doesNotChange(fn, obj, 'val');
    *
    * @name doesNotChange
    * @param {Function} modifier function
    * @param {Object} object or getter function
    * @param {String} property name _optional_
    * @param {String} message _optional_
    * @namespace Assert
    * @api public
    */
 
   assert.doesNotChange = function (fn, obj, prop, msg) {
     if (arguments.length === 3 && typeof obj === 'function') {
       msg = prop;
       prop = null;
     }
 
     return new Assertion(fn, msg, assert.doesNotChange, true)
       .to.not.change(obj, prop);
   }
 
   /**
    * ### .changesButNotBy(function, object, property, delta, [message])
    *
    * Asserts that a function does not change the value of a property or of a function's return value by an amount (delta)
    *
    *     var obj = { val: 10 };
    *     var fn = function() { obj.val += 10 };
    *     assert.changesButNotBy(fn, obj, 'val', 5);
    *
    * @name changesButNotBy
    * @param {Function} modifier function
    * @param {Object} object or getter function
    * @param {String} property name _optional_
    * @param {Number} change amount (delta)
    * @param {String} message _optional_
    * @namespace Assert
    * @api public
    */
 
   assert.changesButNotBy = function (fn, obj, prop, delta, msg) {
     if (arguments.length === 4 && typeof obj === 'function') {
       var tmpMsg = delta;
       delta = prop;
       msg = tmpMsg;
     } else if (arguments.length === 3) {
       delta = prop;
       prop = null;
     }
 
     new Assertion(fn, msg, assert.changesButNotBy, true)
       .to.change(obj, prop).but.not.by(delta);
   }
 
   /**
    * ### .increases(function, object, property, [message])
    *
    * Asserts that a function increases a numeric object property.
    *
    *     var obj = { val: 10 };
    *     var fn = function() { obj.val = 13 };
    *     assert.increases(fn, obj, 'val');
    *
    * @name increases
    * @param {Function} modifier function
    * @param {Object} object or getter function
    * @param {String} property name _optional_
    * @param {String} message _optional_
    * @namespace Assert
    * @api public
    */
 
   assert.increases = function (fn, obj, prop, msg) {
     if (arguments.length === 3 && typeof obj === 'function') {
       msg = prop;
       prop = null;
     }
 
     return new Assertion(fn, msg, assert.increases, true)
       .to.increase(obj, prop);
   }
 
   /**
    * ### .increasesBy(function, object, property, delta, [message])
    *
    * Asserts that a function increases a numeric object property or a function's return value by an amount (delta).
    *
    *     var obj = { val: 10 };
    *     var fn = function() { obj.val += 10 };
    *     assert.increasesBy(fn, obj, 'val', 10);
    *
    * @name increasesBy
    * @param {Function} modifier function
    * @param {Object} object or getter function
    * @param {String} property name _optional_
    * @param {Number} change amount (delta)
    * @param {String} message _optional_
    * @namespace Assert
    * @api public
    */
 
   assert.increasesBy = function (fn, obj, prop, delta, msg) {
     if (arguments.length === 4 && typeof obj === 'function') {
       var tmpMsg = delta;
       delta = prop;
       msg = tmpMsg;
     } else if (arguments.length === 3) {
       delta = prop;
       prop = null;
     }
 
     new Assertion(fn, msg, assert.increasesBy, true)
       .to.increase(obj, prop).by(delta);
   }
 
   /**
    * ### .doesNotIncrease(function, object, property, [message])
    *
    * Asserts that a function does not increase a numeric object property.
    *
    *     var obj = { val: 10 };
    *     var fn = function() { obj.val = 8 };
    *     assert.doesNotIncrease(fn, obj, 'val');
    *
    * @name doesNotIncrease
    * @param {Function} modifier function
    * @param {Object} object or getter function
    * @param {String} property name _optional_
    * @param {String} message _optional_
    * @namespace Assert
    * @api public
    */
 
   assert.doesNotIncrease = function (fn, obj, prop, msg) {
     if (arguments.length === 3 && typeof obj === 'function') {
       msg = prop;
       prop = null;
     }
 
     return new Assertion(fn, msg, assert.doesNotIncrease, true)
       .to.not.increase(obj, prop);
   }
 
   /**
    * ### .increasesButNotBy(function, object, property, delta, [message])
    *
    * Asserts that a function does not increase a numeric object property or function's return value by an amount (delta).
    *
    *     var obj = { val: 10 };
    *     var fn = function() { obj.val = 15 };
    *     assert.increasesButNotBy(fn, obj, 'val', 10);
    *
    * @name increasesButNotBy
    * @param {Function} modifier function
    * @param {Object} object or getter function
    * @param {String} property name _optional_
    * @param {Number} change amount (delta)
    * @param {String} message _optional_
    * @namespace Assert
    * @api public
    */
 
   assert.increasesButNotBy = function (fn, obj, prop, delta, msg) {
     if (arguments.length === 4 && typeof obj === 'function') {
       var tmpMsg = delta;
       delta = prop;
       msg = tmpMsg;
     } else if (arguments.length === 3) {
       delta = prop;
       prop = null;
     }
 
     new Assertion(fn, msg, assert.increasesButNotBy, true)
       .to.increase(obj, prop).but.not.by(delta);
   }
 
   /**
    * ### .decreases(function, object, property, [message])
    *
    * Asserts that a function decreases a numeric object property.
    *
    *     var obj = { val: 10 };
    *     var fn = function() { obj.val = 5 };
    *     assert.decreases(fn, obj, 'val');
    *
    * @name decreases
    * @param {Function} modifier function
    * @param {Object} object or getter function
    * @param {String} property name _optional_
    * @param {String} message _optional_
    * @namespace Assert
    * @api public
    */
 
   assert.decreases = function (fn, obj, prop, msg) {
     if (arguments.length === 3 && typeof obj === 'function') {
       msg = prop;
       prop = null;
     }
 
     return new Assertion(fn, msg, assert.decreases, true)
       .to.decrease(obj, prop);
   }
 
   /**
    * ### .decreasesBy(function, object, property, delta, [message])
    *
    * Asserts that a function decreases a numeric object property or a function's return value by an amount (delta)
    *
    *     var obj = { val: 10 };
    *     var fn = function() { obj.val -= 5 };
    *     assert.decreasesBy(fn, obj, 'val', 5);
    *
    * @name decreasesBy
    * @param {Function} modifier function
    * @param {Object} object or getter function
    * @param {String} property name _optional_
    * @param {Number} change amount (delta)
    * @param {String} message _optional_
    * @namespace Assert
    * @api public
    */
 
   assert.decreasesBy = function (fn, obj, prop, delta, msg) {
     if (arguments.length === 4 && typeof obj === 'function') {
       var tmpMsg = delta;
       delta = prop;
       msg = tmpMsg;
     } else if (arguments.length === 3) {
       delta = prop;
       prop = null;
     }
 
     new Assertion(fn, msg, assert.decreasesBy, true)
       .to.decrease(obj, prop).by(delta);
   }
 
   /**
    * ### .doesNotDecrease(function, object, property, [message])
    *
    * Asserts that a function does not decreases a numeric object property.
    *
    *     var obj = { val: 10 };
    *     var fn = function() { obj.val = 15 };
    *     assert.doesNotDecrease(fn, obj, 'val');
    *
    * @name doesNotDecrease
    * @param {Function} modifier function
    * @param {Object} object or getter function
    * @param {String} property name _optional_
    * @param {String} message _optional_
    * @namespace Assert
    * @api public
    */
 
   assert.doesNotDecrease = function (fn, obj, prop, msg) {
     if (arguments.length === 3 && typeof obj === 'function') {
       msg = prop;
       prop = null;
     }
 
     return new Assertion(fn, msg, assert.doesNotDecrease, true)
       .to.not.decrease(obj, prop);
   }
 
   /**
    * ### .doesNotDecreaseBy(function, object, property, delta, [message])
    *
    * Asserts that a function does not decreases a numeric object property or a function's return value by an amount (delta)
    *
    *     var obj = { val: 10 };
    *     var fn = function() { obj.val = 5 };
    *     assert.doesNotDecreaseBy(fn, obj, 'val', 1);
    *
    * @name doesNotDecreaseBy
    * @param {Function} modifier function
    * @param {Object} object or getter function
    * @param {String} property name _optional_
    * @param {Number} change amount (delta)
    * @param {String} message _optional_
    * @namespace Assert
    * @api public
    */
 
   assert.doesNotDecreaseBy = function (fn, obj, prop, delta, msg) {
     if (arguments.length === 4 && typeof obj === 'function') {
       var tmpMsg = delta;
       delta = prop;
       msg = tmpMsg;
     } else if (arguments.length === 3) {
       delta = prop;
       prop = null;
     }
 
     return new Assertion(fn, msg, assert.doesNotDecreaseBy, true)
       .to.not.decrease(obj, prop).by(delta);
   }
 
   /**
    * ### .decreasesButNotBy(function, object, property, delta, [message])
    *
    * Asserts that a function does not decreases a numeric object property or a function's return value by an amount (delta)
    *
    *     var obj = { val: 10 };
    *     var fn = function() { obj.val = 5 };
    *     assert.decreasesButNotBy(fn, obj, 'val', 1);
    *
    * @name decreasesButNotBy
    * @param {Function} modifier function
    * @param {Object} object or getter function
    * @param {String} property name _optional_
    * @param {Number} change amount (delta)
    * @param {String} message _optional_
    * @namespace Assert
    * @api public
    */
 
   assert.decreasesButNotBy = function (fn, obj, prop, delta, msg) {
     if (arguments.length === 4 && typeof obj === 'function') {
       var tmpMsg = delta;
       delta = prop;
       msg = tmpMsg;
     } else if (arguments.length === 3) {
       delta = prop;
       prop = null;
     }
 
     new Assertion(fn, msg, assert.decreasesButNotBy, true)
       .to.decrease(obj, prop).but.not.by(delta);
   }
 
   /*!
    * ### .ifError(object)
    *
    * Asserts if value is not a false value, and throws if it is a true value.
    * This is added to allow for chai to be a drop-in replacement for Node's
    * assert class.
    *
    *     var err = new Error('I am a custom error');
    *     assert.ifError(err); // Rethrows err!
    *
    * @name ifError
    * @param {Object} object
    * @namespace Assert
    * @api public
    */
 
   assert.ifError = function (val) {
     if (val) {
       throw(val);
     }
   };
 
   /**
    * ### .isExtensible(object)
    *
    * Asserts that `object` is extensible (can have new properties added to it).
    *
    *     assert.isExtensible({});
    *
    * @name isExtensible
    * @alias extensible
    * @param {Object} object
    * @param {String} message _optional_
    * @namespace Assert
    * @api public
    */
 
   assert.isExtensible = function (obj, msg) {
     new Assertion(obj, msg, assert.isExtensible, true).to.be.extensible;
   };
 
   /**
    * ### .isNotExtensible(object)
    *
    * Asserts that `object` is _not_ extensible.
    *
    *     var nonExtensibleObject = Object.preventExtensions({});
    *     var sealedObject = Object.seal({});
    *     var frozenObject = Object.freeze({});
    *
    *     assert.isNotExtensible(nonExtensibleObject);
    *     assert.isNotExtensible(sealedObject);
    *     assert.isNotExtensible(frozenObject);
    *
    * @name isNotExtensible
    * @alias notExtensible
    * @param {Object} object
    * @param {String} message _optional_
    * @namespace Assert
    * @api public
    */
 
   assert.isNotExtensible = function (obj, msg) {
     new Assertion(obj, msg, assert.isNotExtensible, true).to.not.be.extensible;
   };
 
   /**
    * ### .isSealed(object)
    *
    * Asserts that `object` is sealed (cannot have new properties added to it
    * and its existing properties cannot be removed).
    *
    *     var sealedObject = Object.seal({});
    *     var frozenObject = Object.seal({});
    *
    *     assert.isSealed(sealedObject);
    *     assert.isSealed(frozenObject);
    *
    * @name isSealed
    * @alias sealed
    * @param {Object} object
    * @param {String} message _optional_
    * @namespace Assert
    * @api public
    */
 
   assert.isSealed = function (obj, msg) {
     new Assertion(obj, msg, assert.isSealed, true).to.be.sealed;
   };
 
   /**
    * ### .isNotSealed(object)
    *
    * Asserts that `object` is _not_ sealed.
    *
    *     assert.isNotSealed({});
    *
    * @name isNotSealed
    * @alias notSealed
    * @param {Object} object
    * @param {String} message _optional_
    * @namespace Assert
    * @api public
    */
 
   assert.isNotSealed = function (obj, msg) {
     new Assertion(obj, msg, assert.isNotSealed, true).to.not.be.sealed;
   };
 
   /**
    * ### .isFrozen(object)
    *
    * Asserts that `object` is frozen (cannot have new properties added to it
    * and its existing properties cannot be modified).
    *
    *     var frozenObject = Object.freeze({});
    *     assert.frozen(frozenObject);
    *
    * @name isFrozen
    * @alias frozen
    * @param {Object} object
    * @param {String} message _optional_
    * @namespace Assert
    * @api public
    */
 
   assert.isFrozen = function (obj, msg) {
     new Assertion(obj, msg, assert.isFrozen, true).to.be.frozen;
   };
 
   /**
    * ### .isNotFrozen(object)
    *
    * Asserts that `object` is _not_ frozen.
    *
    *     assert.isNotFrozen({});
    *
    * @name isNotFrozen
    * @alias notFrozen
    * @param {Object} object
    * @param {String} message _optional_
    * @namespace Assert
    * @api public
    */
 
   assert.isNotFrozen = function (obj, msg) {
     new Assertion(obj, msg, assert.isNotFrozen, true).to.not.be.frozen;
   };
 
   /**
    * ### .isEmpty(target)
    *
    * Asserts that the target does not contain any values.
    * For arrays and strings, it checks the `length` property.
    * For `Map` and `Set` instances, it checks the `size` property.
    * For non-function objects, it gets the count of own
    * enumerable string keys.
    *
    *     assert.isEmpty([]);
    *     assert.isEmpty('');
    *     assert.isEmpty(new Map);
    *     assert.isEmpty({});
    *
    * @name isEmpty
    * @alias empty
    * @param {Object|Array|String|Map|Set} target
    * @param {String} message _optional_
    * @namespace Assert
    * @api public
    */
 
   assert.isEmpty = function(val, msg) {
     new Assertion(val, msg, assert.isEmpty, true).to.be.empty;
   };
 
   /**
    * ### .isNotEmpty(target)
    *
    * Asserts that the target contains values.
    * For arrays and strings, it checks the `length` property.
    * For `Map` and `Set` instances, it checks the `size` property.
    * For non-function objects, it gets the count of own
    * enumerable string keys.
    *
    *     assert.isNotEmpty([1, 2]);
    *     assert.isNotEmpty('34');
    *     assert.isNotEmpty(new Set([5, 6]));
    *     assert.isNotEmpty({ key: 7 });
    *
    * @name isNotEmpty
    * @alias notEmpty
    * @param {Object|Array|String|Map|Set} target
    * @param {String} message _optional_
    * @namespace Assert
    * @api public
    */
 
   assert.isNotEmpty = function(val, msg) {
     new Assertion(val, msg, assert.isNotEmpty, true).to.not.be.empty;
   };
 
   /*!
    * Aliases.
    */
 
   (function alias(name, as){
     assert[as] = assert[name];
     return alias;
   })
   ('isOk', 'ok')
   ('isNotOk', 'notOk')
   ('throws', 'throw')
   ('throws', 'Throw')
   ('isExtensible', 'extensible')
   ('isNotExtensible', 'notExtensible')
   ('isSealed', 'sealed')
   ('isNotSealed', 'notSealed')
   ('isFrozen', 'frozen')
   ('isNotFrozen', 'notFrozen')
   ('isEmpty', 'empty')
   ('isNotEmpty', 'notEmpty');
 };
 
 },{}],7:[function(require,module,exports){
 /*!
  * chai
  * Copyright(c) 2011-2014 Jake Luer <jake@alogicalparadox.com>
  * MIT Licensed
  */
 
 module.exports = function (chai, util) {
   chai.expect = function (val, message) {
     return new chai.Assertion(val, message);
   };
 
   /**
    * ### .fail([message])
    * ### .fail(actual, expected, [message], [operator])
    *
    * Throw a failure.
    *
    *     expect.fail();
    *     expect.fail("custom error message");
    *     expect.fail(1, 2);
    *     expect.fail(1, 2, "custom error message");
    *     expect.fail(1, 2, "custom error message", ">");
    *     expect.fail(1, 2, undefined, ">");
    *
    * @name fail
    * @param {Mixed} actual
    * @param {Mixed} expected
    * @param {String} message
    * @param {String} operator
    * @namespace BDD
    * @api public
    */
 
   chai.expect.fail = function (actual, expected, message, operator) {
     if (arguments.length < 2) {
         message = actual;
         actual = undefined;
     }
 
     message = message || 'expect.fail()';
     throw new chai.AssertionError(message, {
         actual: actual
       , expected: expected
       , operator: operator
     }, chai.expect.fail);
   };
 };
 
 },{}],8:[function(require,module,exports){
 /*!
  * chai
  * Copyright(c) 2011-2014 Jake Luer <jake@alogicalparadox.com>
  * MIT Licensed
  */
 
 module.exports = function (chai, util) {
   var Assertion = chai.Assertion;
 
   function loadShould () {
     // explicitly define this method as function as to have it's name to include as `ssfi`
     function shouldGetter() {
       if (this instanceof String
           || this instanceof Number
           || this instanceof Boolean
           || typeof Symbol === 'function' && this instanceof Symbol
           || typeof BigInt === 'function' && this instanceof BigInt) {
         return new Assertion(this.valueOf(), null, shouldGetter);
       }
       return new Assertion(this, null, shouldGetter);
     }
     function shouldSetter(value) {
       // See https://github.com/chaijs/chai/issues/86: this makes
       // `whatever.should = someValue` actually set `someValue`, which is
       // especially useful for `global.should = require('chai').should()`.
       //
       // Note that we have to use [[DefineProperty]] instead of [[Put]]
       // since otherwise we would trigger this very setter!
       Object.defineProperty(this, 'should', {
         value: value,
         enumerable: true,
         configurable: true,
         writable: true
       });
     }
     // modify Object.prototype to have `should`
     Object.defineProperty(Object.prototype, 'should', {
       set: shouldSetter
       , get: shouldGetter
       , configurable: true
     });
 
     var should = {};
 
     /**
      * ### .fail([message])
      * ### .fail(actual, expected, [message], [operator])
      *
      * Throw a failure.
      *
      *     should.fail();
      *     should.fail("custom error message");
      *     should.fail(1, 2);
      *     should.fail(1, 2, "custom error message");
      *     should.fail(1, 2, "custom error message", ">");
      *     should.fail(1, 2, undefined, ">");
      *
      *
      * @name fail
      * @param {Mixed} actual
      * @param {Mixed} expected
      * @param {String} message
      * @param {String} operator
      * @namespace BDD
      * @api public
      */
 
     should.fail = function (actual, expected, message, operator) {
       if (arguments.length < 2) {
           message = actual;
           actual = undefined;
       }
 
       message = message || 'should.fail()';
       throw new chai.AssertionError(message, {
           actual: actual
         , expected: expected
         , operator: operator
       }, should.fail);
     };
 
     /**
      * ### .equal(actual, expected, [message])
      *
      * Asserts non-strict equality (`==`) of `actual` and `expected`.
      *
      *     should.equal(3, '3', '== coerces values to strings');
      *
      * @name equal
      * @param {Mixed} actual
      * @param {Mixed} expected
      * @param {String} message
      * @namespace Should
      * @api public
      */
 
     should.equal = function (val1, val2, msg) {
       new Assertion(val1, msg).to.equal(val2);
     };
 
     /**
      * ### .throw(function, [constructor/string/regexp], [string/regexp], [message])
      *
      * Asserts that `function` will throw an error that is an instance of
      * `constructor`, or alternately that it will throw an error with message
      * matching `regexp`.
      *
      *     should.throw(fn, 'function throws a reference error');
      *     should.throw(fn, /function throws a reference error/);
      *     should.throw(fn, ReferenceError);
      *     should.throw(fn, ReferenceError, 'function throws a reference error');
      *     should.throw(fn, ReferenceError, /function throws a reference error/);
      *
      * @name throw
      * @alias Throw
      * @param {Function} function
      * @param {ErrorConstructor} constructor
      * @param {RegExp} regexp
      * @param {String} message
      * @see https://developer.mozilla.org/en/JavaScript/Reference/Global_Objects/Error#Error_types
      * @namespace Should
      * @api public
      */
 
     should.Throw = function (fn, errt, errs, msg) {
       new Assertion(fn, msg).to.Throw(errt, errs);
     };
 
     /**
      * ### .exist
      *
      * Asserts that the target is neither `null` nor `undefined`.
      *
      *     var foo = 'hi';
      *
      *     should.exist(foo, 'foo exists');
      *
      * @name exist
      * @namespace Should
      * @api public
      */
 
     should.exist = function (val, msg) {
       new Assertion(val, msg).to.exist;
     }
 
     // negation
     should.not = {}
 
     /**
      * ### .not.equal(actual, expected, [message])
      *
      * Asserts non-strict inequality (`!=`) of `actual` and `expected`.
      *
      *     should.not.equal(3, 4, 'these numbers are not equal');
      *
      * @name not.equal
      * @param {Mixed} actual
      * @param {Mixed} expected
      * @param {String} message
      * @namespace Should
      * @api public
      */
 
     should.not.equal = function (val1, val2, msg) {
       new Assertion(val1, msg).to.not.equal(val2);
     };
 
     /**
      * ### .throw(function, [constructor/regexp], [message])
      *
      * Asserts that `function` will _not_ throw an error that is an instance of
      * `constructor`, or alternately that it will not throw an error with message
      * matching `regexp`.
      *
      *     should.not.throw(fn, Error, 'function does not throw');
      *
      * @name not.throw
      * @alias not.Throw
      * @param {Function} function
      * @param {ErrorConstructor} constructor
      * @param {RegExp} regexp
      * @param {String} message
      * @see https://developer.mozilla.org/en/JavaScript/Reference/Global_Objects/Error#Error_types
      * @namespace Should
      * @api public
      */
 
     should.not.Throw = function (fn, errt, errs, msg) {
       new Assertion(fn, msg).to.not.Throw(errt, errs);
     };
 
     /**
      * ### .not.exist
      *
      * Asserts that the target is neither `null` nor `undefined`.
      *
      *     var bar = null;
      *
      *     should.not.exist(bar, 'bar does not exist');
      *
      * @name not.exist
      * @namespace Should
      * @api public
      */
 
     should.not.exist = function (val, msg) {
       new Assertion(val, msg).to.not.exist;
     }
 
     should['throw'] = should['Throw'];
     should.not['throw'] = should.not['Throw'];
 
     return should;
   };
 
   chai.should = loadShould;
   chai.Should = loadShould;
 };
 
 },{}],9:[function(require,module,exports){
 /*!
  * Chai - addChainingMethod utility
  * Copyright(c) 2012-2014 Jake Luer <jake@alogicalparadox.com>
  * MIT Licensed
  */
 
 /*!
  * Module dependencies
  */
 
 var addLengthGuard = require('./addLengthGuard');
 var chai = require('../../chai');
 var flag = require('./flag');
 var proxify = require('./proxify');
 var transferFlags = require('./transferFlags');
 
 /*!
  * Module variables
  */
 
 // Check whether `Object.setPrototypeOf` is supported
 var canSetPrototype = typeof Object.setPrototypeOf === 'function';
 
 // Without `Object.setPrototypeOf` support, this module will need to add properties to a function.
 // However, some of functions' own props are not configurable and should be skipped.
 var testFn = function() {};
 var excludeNames = Object.getOwnPropertyNames(testFn).filter(function(name) {
   var propDesc = Object.getOwnPropertyDescriptor(testFn, name);
 
   // Note: PhantomJS 1.x includes `callee` as one of `testFn`'s own properties,
   // but then returns `undefined` as the property descriptor for `callee`. As a
   // workaround, we perform an otherwise unnecessary type-check for `propDesc`,
   // and then filter it out if it's not an object as it should be.
   if (typeof propDesc !== 'object')
     return true;
 
   return !propDesc.configurable;
 });
 
 // Cache `Function` properties
 var call  = Function.prototype.call,
     apply = Function.prototype.apply;
 
 /**
  * ### .addChainableMethod(ctx, name, method, chainingBehavior)
  *
  * Adds a method to an object, such that the method can also be chained.
  *
  *     utils.addChainableMethod(chai.Assertion.prototype, 'foo', function (str) {
  *       var obj = utils.flag(this, 'object');
  *       new chai.Assertion(obj).to.be.equal(str);
  *     });
  *
  * Can also be accessed directly from `chai.Assertion`.
  *
  *     chai.Assertion.addChainableMethod('foo', fn, chainingBehavior);
  *
  * The result can then be used as both a method assertion, executing both `method` and
  * `chainingBehavior`, or as a language chain, which only executes `chainingBehavior`.
  *
  *     expect(fooStr).to.be.foo('bar');
  *     expect(fooStr).to.be.foo.equal('foo');
  *
  * @param {Object} ctx object to which the method is added
  * @param {String} name of method to add
  * @param {Function} method function to be used for `name`, when called
  * @param {Function} chainingBehavior function to be called every time the property is accessed
  * @namespace Utils
  * @name addChainableMethod
  * @api public
  */
 
 module.exports = function addChainableMethod(ctx, name, method, chainingBehavior) {
   if (typeof chainingBehavior !== 'function') {
     chainingBehavior = function () { };
   }
 
   var chainableBehavior = {
       method: method
     , chainingBehavior: chainingBehavior
   };
 
   // save the methods so we can overwrite them later, if we need to.
   if (!ctx.__methods) {
     ctx.__methods = {};
   }
   ctx.__methods[name] = chainableBehavior;
 
   Object.defineProperty(ctx, name,
     { get: function chainableMethodGetter() {
         chainableBehavior.chainingBehavior.call(this);
 
         var chainableMethodWrapper = function () {
           // Setting the `ssfi` flag to `chainableMethodWrapper` causes this
           // function to be the starting point for removing implementation
           // frames from the stack trace of a failed assertion.
           //
           // However, we only want to use this function as the starting point if
           // the `lockSsfi` flag isn't set.
           //
           // If the `lockSsfi` flag is set, then this assertion is being
           // invoked from inside of another assertion. In this case, the `ssfi`
           // flag has already been set by the outer assertion.
           //
           // Note that overwriting a chainable method merely replaces the saved
           // methods in `ctx.__methods` instead of completely replacing the
           // overwritten assertion. Therefore, an overwriting assertion won't
           // set the `ssfi` or `lockSsfi` flags.
           if (!flag(this, 'lockSsfi')) {
             flag(this, 'ssfi', chainableMethodWrapper);
           }
 
           var result = chainableBehavior.method.apply(this, arguments);
           if (result !== undefined) {
             return result;
           }
 
           var newAssertion = new chai.Assertion();
           transferFlags(this, newAssertion);
           return newAssertion;
         };
 
         addLengthGuard(chainableMethodWrapper, name, true);
 
         // Use `Object.setPrototypeOf` if available
         if (canSetPrototype) {
           // Inherit all properties from the object by replacing the `Function` prototype
           var prototype = Object.create(this);
           // Restore the `call` and `apply` methods from `Function`
           prototype.call = call;
           prototype.apply = apply;
           Object.setPrototypeOf(chainableMethodWrapper, prototype);
         }
         // Otherwise, redefine all properties (slow!)
         else {
           var asserterNames = Object.getOwnPropertyNames(ctx);
           asserterNames.forEach(function (asserterName) {
             if (excludeNames.indexOf(asserterName) !== -1) {
               return;
             }
 
             var pd = Object.getOwnPropertyDescriptor(ctx, asserterName);
             Object.defineProperty(chainableMethodWrapper, asserterName, pd);
           });
         }
 
         transferFlags(this, chainableMethodWrapper);
         return proxify(chainableMethodWrapper);
       }
     , configurable: true
   });
 };
 
 },{"../../chai":2,"./addLengthGuard":10,"./flag":15,"./proxify":31,"./transferFlags":33}],10:[function(require,module,exports){
 var fnLengthDesc = Object.getOwnPropertyDescriptor(function () {}, 'length');
 
 /*!
  * Chai - addLengthGuard utility
  * Copyright(c) 2012-2014 Jake Luer <jake@alogicalparadox.com>
  * MIT Licensed
  */
 
 /**
  * ### .addLengthGuard(fn, assertionName, isChainable)
  *
  * Define `length` as a getter on the given uninvoked method assertion. The
  * getter acts as a guard against chaining `length` directly off of an uninvoked
  * method assertion, which is a problem because it references `function`'s
  * built-in `length` property instead of Chai's `length` assertion. When the
  * getter catches the user making this mistake, it throws an error with a
  * helpful message.
  *
  * There are two ways in which this mistake can be made. The first way is by
  * chaining the `length` assertion directly off of an uninvoked chainable
  * method. In this case, Chai suggests that the user use `lengthOf` instead. The
  * second way is by chaining the `length` assertion directly off of an uninvoked
  * non-chainable method. Non-chainable methods must be invoked prior to
  * chaining. In this case, Chai suggests that the user consult the docs for the
  * given assertion.
  *
  * If the `length` property of functions is unconfigurable, then return `fn`
  * without modification.
  *
  * Note that in ES6, the function's `length` property is configurable, so once
  * support for legacy environments is dropped, Chai's `length` property can
  * replace the built-in function's `length` property, and this length guard will
  * no longer be necessary. In the mean time, maintaining consistency across all
  * environments is the priority.
  *
  * @param {Function} fn
  * @param {String} assertionName
  * @param {Boolean} isChainable
  * @namespace Utils
  * @name addLengthGuard
  */
 
 module.exports = function addLengthGuard (fn, assertionName, isChainable) {
   if (!fnLengthDesc.configurable) return fn;
 
   Object.defineProperty(fn, 'length', {
     get: function () {
       if (isChainable) {
         throw Error('Invalid Chai property: ' + assertionName + '.length. Due' +
           ' to a compatibility issue, "length" cannot directly follow "' +
           assertionName + '". Use "' + assertionName + '.lengthOf" instead.');
       }
 
       throw Error('Invalid Chai property: ' + assertionName + '.length. See' +
         ' docs for proper usage of "' + assertionName + '".');
     }
   });
 
   return fn;
 };
 
 },{}],11:[function(require,module,exports){
 /*!
  * Chai - addMethod utility
  * Copyright(c) 2012-2014 Jake Luer <jake@alogicalparadox.com>
  * MIT Licensed
  */
 
 var addLengthGuard = require('./addLengthGuard');
 var chai = require('../../chai');
 var flag = require('./flag');
 var proxify = require('./proxify');
 var transferFlags = require('./transferFlags');
 
 /**
  * ### .addMethod(ctx, name, method)
  *
  * Adds a method to the prototype of an object.
  *
  *     utils.addMethod(chai.Assertion.prototype, 'foo', function (str) {
  *       var obj = utils.flag(this, 'object');
  *       new chai.Assertion(obj).to.be.equal(str);
  *     });
  *
  * Can also be accessed directly from `chai.Assertion`.
  *
  *     chai.Assertion.addMethod('foo', fn);
  *
  * Then can be used as any other assertion.
  *
  *     expect(fooStr).to.be.foo('bar');
  *
  * @param {Object} ctx object to which the method is added
  * @param {String} name of method to add
  * @param {Function} method function to be used for name
  * @namespace Utils
  * @name addMethod
  * @api public
  */
 
 module.exports = function addMethod(ctx, name, method) {
   var methodWrapper = function () {
     // Setting the `ssfi` flag to `methodWrapper` causes this function to be the
     // starting point for removing implementation frames from the stack trace of
     // a failed assertion.
     //
     // However, we only want to use this function as the starting point if the
     // `lockSsfi` flag isn't set.
     //
     // If the `lockSsfi` flag is set, then either this assertion has been
     // overwritten by another assertion, or this assertion is being invoked from
     // inside of another assertion. In the first case, the `ssfi` flag has
     // already been set by the overwriting assertion. In the second case, the
     // `ssfi` flag has already been set by the outer assertion.
     if (!flag(this, 'lockSsfi')) {
       flag(this, 'ssfi', methodWrapper);
     }
 
     var result = method.apply(this, arguments);
     if (result !== undefined)
       return result;
 
     var newAssertion = new chai.Assertion();
     transferFlags(this, newAssertion);
     return newAssertion;
   };
 
   addLengthGuard(methodWrapper, name, false);
   ctx[name] = proxify(methodWrapper, name);
 };
 
 },{"../../chai":2,"./addLengthGuard":10,"./flag":15,"./proxify":31,"./transferFlags":33}],12:[function(require,module,exports){
 /*!
  * Chai - addProperty utility
  * Copyright(c) 2012-2014 Jake Luer <jake@alogicalparadox.com>
  * MIT Licensed
  */
 
 var chai = require('../../chai');
 var flag = require('./flag');
 var isProxyEnabled = require('./isProxyEnabled');
 var transferFlags = require('./transferFlags');
 
 /**
  * ### .addProperty(ctx, name, getter)
  *
  * Adds a property to the prototype of an object.
  *
  *     utils.addProperty(chai.Assertion.prototype, 'foo', function () {
  *       var obj = utils.flag(this, 'object');
  *       new chai.Assertion(obj).to.be.instanceof(Foo);
  *     });
  *
  * Can also be accessed directly from `chai.Assertion`.
  *
  *     chai.Assertion.addProperty('foo', fn);
  *
  * Then can be used as any other assertion.
  *
  *     expect(myFoo).to.be.foo;
  *
  * @param {Object} ctx object to which the property is added
  * @param {String} name of property to add
  * @param {Function} getter function to be used for name
  * @namespace Utils
  * @name addProperty
  * @api public
  */
 
 module.exports = function addProperty(ctx, name, getter) {
   getter = getter === undefined ? function () {} : getter;
 
   Object.defineProperty(ctx, name,
     { get: function propertyGetter() {
         // Setting the `ssfi` flag to `propertyGetter` causes this function to
         // be the starting point for removing implementation frames from the
         // stack trace of a failed assertion.
         //
         // However, we only want to use this function as the starting point if
         // the `lockSsfi` flag isn't set and proxy protection is disabled.
         //
         // If the `lockSsfi` flag is set, then either this assertion has been
         // overwritten by another assertion, or this assertion is being invoked
         // from inside of another assertion. In the first case, the `ssfi` flag
         // has already been set by the overwriting assertion. In the second
         // case, the `ssfi` flag has already been set by the outer assertion.
         //
         // If proxy protection is enabled, then the `ssfi` flag has already been
         // set by the proxy getter.
         if (!isProxyEnabled() && !flag(this, 'lockSsfi')) {
           flag(this, 'ssfi', propertyGetter);
         }
 
         var result = getter.call(this);
         if (result !== undefined)
           return result;
 
         var newAssertion = new chai.Assertion();
         transferFlags(this, newAssertion);
         return newAssertion;
       }
     , configurable: true
   });
 };
 
 },{"../../chai":2,"./flag":15,"./isProxyEnabled":26,"./transferFlags":33}],13:[function(require,module,exports){
 /*!
  * Chai - compareByInspect utility
  * Copyright(c) 2011-2016 Jake Luer <jake@alogicalparadox.com>
  * MIT Licensed
  */
 
 /*!
  * Module dependencies
  */
 
 var inspect = require('./inspect');
 
 /**
  * ### .compareByInspect(mixed, mixed)
  *
  * To be used as a compareFunction with Array.prototype.sort. Compares elements
  * using inspect instead of default behavior of using toString so that Symbols
  * and objects with irregular/missing toString can still be sorted without a
  * TypeError.
  *
  * @param {Mixed} first element to compare
  * @param {Mixed} second element to compare
  * @returns {Number} -1 if 'a' should come before 'b'; otherwise 1
  * @name compareByInspect
  * @namespace Utils
  * @api public
  */
 
 module.exports = function compareByInspect(a, b) {
   return inspect(a) < inspect(b) ? -1 : 1;
 };
 
 },{"./inspect":24}],14:[function(require,module,exports){
 /*!
  * Chai - expectTypes utility
  * Copyright(c) 2012-2014 Jake Luer <jake@alogicalparadox.com>
  * MIT Licensed
  */
 
 /**
  * ### .expectTypes(obj, types)
  *
  * Ensures that the object being tested against is of a valid type.
  *
  *     utils.expectTypes(this, ['array', 'object', 'string']);
  *
  * @param {Mixed} obj constructed Assertion
  * @param {Array} type A list of allowed types for this assertion
  * @namespace Utils
  * @name expectTypes
  * @api public
  */
 
 var AssertionError = require('assertion-error');
 var flag = require('./flag');
 var type = require('type-detect');
 
 module.exports = function expectTypes(obj, types) {
   var flagMsg = flag(obj, 'message');
   var ssfi = flag(obj, 'ssfi');
 
   flagMsg = flagMsg ? flagMsg + ': ' : '';
 
   obj = flag(obj, 'object');
   types = types.map(function (t) { return t.toLowerCase(); });
   types.sort();
 
   // Transforms ['lorem', 'ipsum'] into 'a lorem, or an ipsum'
   var str = types.map(function (t, index) {
     var art = ~[ 'a', 'e', 'i', 'o', 'u' ].indexOf(t.charAt(0)) ? 'an' : 'a';
     var or = types.length > 1 && index === types.length - 1 ? 'or ' : '';
     return or + art + ' ' + t;
   }).join(', ');
 
   var objType = type(obj).toLowerCase();
 
   if (!types.some(function (expected) { return objType === expected; })) {
     throw new AssertionError(
       flagMsg + 'object tested must be ' + str + ', but ' + objType + ' given',
       undefined,
       ssfi
     );
   }
 };
 
 },{"./flag":15,"assertion-error":34,"type-detect":39}],15:[function(require,module,exports){
 /*!
  * Chai - flag utility
  * Copyright(c) 2012-2014 Jake Luer <jake@alogicalparadox.com>
  * MIT Licensed
  */
 
 /**
  * ### .flag(object, key, [value])
  *
  * Get or set a flag value on an object. If a
  * value is provided it will be set, else it will
  * return the currently set value or `undefined` if
  * the value is not set.
  *
  *     utils.flag(this, 'foo', 'bar'); // setter
  *     utils.flag(this, 'foo'); // getter, returns `bar`
  *
  * @param {Object} object constructed Assertion
  * @param {String} key
  * @param {Mixed} value (optional)
  * @namespace Utils
  * @name flag
  * @api private
  */
 
 module.exports = function flag(obj, key, value) {
   var flags = obj.__flags || (obj.__flags = Object.create(null));
   if (arguments.length === 3) {
     flags[key] = value;
   } else {
     return flags[key];
   }
 };
 
 },{}],16:[function(require,module,exports){
 /*!
  * Chai - getActual utility
  * Copyright(c) 2012-2014 Jake Luer <jake@alogicalparadox.com>
  * MIT Licensed
  */
 
 /**
  * ### .getActual(object, [actual])
  *
  * Returns the `actual` value for an Assertion.
  *
  * @param {Object} object (constructed Assertion)
  * @param {Arguments} chai.Assertion.prototype.assert arguments
  * @namespace Utils
  * @name getActual
  */
 
 module.exports = function getActual(obj, args) {
   return args.length > 4 ? args[4] : obj._obj;
 };
 
 },{}],17:[function(require,module,exports){
 /*!
  * Chai - getEnumerableProperties utility
  * Copyright(c) 2012-2014 Jake Luer <jake@alogicalparadox.com>
  * MIT Licensed
  */
 
 /**
  * ### .getEnumerableProperties(object)
  *
  * This allows the retrieval of enumerable property names of an object,
  * inherited or not.
  *
  * @param {Object} object
  * @returns {Array}
  * @namespace Utils
  * @name getEnumerableProperties
  * @api public
  */
 
 module.exports = function getEnumerableProperties(object) {
   var result = [];
   for (var name in object) {
     result.push(name);
   }
   return result;
 };
 
 },{}],18:[function(require,module,exports){
 /*!
  * Chai - message composition utility
  * Copyright(c) 2012-2014 Jake Luer <jake@alogicalparadox.com>
  * MIT Licensed
  */
 
 /*!
  * Module dependencies
  */
 
 var flag = require('./flag')
   , getActual = require('./getActual')
   , objDisplay = require('./objDisplay');
 
 /**
  * ### .getMessage(object, message, negateMessage)
  *
  * Construct the error message based on flags
  * and template tags. Template tags will return
  * a stringified inspection of the object referenced.
  *
  * Message template tags:
  * - `#{this}` current asserted object
  * - `#{act}` actual value
  * - `#{exp}` expected value
  *
  * @param {Object} object (constructed Assertion)
  * @param {Arguments} chai.Assertion.prototype.assert arguments
  * @namespace Utils
  * @name getMessage
  * @api public
  */
 
 module.exports = function getMessage(obj, args) {
   var negate = flag(obj, 'negate')
     , val = flag(obj, 'object')
     , expected = args[3]
     , actual = getActual(obj, args)
     , msg = negate ? args[2] : args[1]
     , flagMsg = flag(obj, 'message');
 
   if(typeof msg === "function") msg = msg();
   msg = msg || '';
   msg = msg
     .replace(/#\{this\}/g, function () { return objDisplay(val); })
     .replace(/#\{act\}/g, function () { return objDisplay(actual); })
     .replace(/#\{exp\}/g, function () { return objDisplay(expected); });
 
   return flagMsg ? flagMsg + ': ' + msg : msg;
 };
 
 },{"./flag":15,"./getActual":16,"./objDisplay":27}],19:[function(require,module,exports){
 var type = require('type-detect');
 
 var flag = require('./flag');
 
 function isObjectType(obj) {
   var objectType = type(obj);
   var objectTypes = ['Array', 'Object', 'function'];
 
   return objectTypes.indexOf(objectType) !== -1;
 }
 
 /**
  * ### .getOperator(message)
  *
  * Extract the operator from error message.
  * Operator defined is based on below link
  * https://nodejs.org/api/assert.html#assert_assert.
  *
  * Returns the `operator` or `undefined` value for an Assertion.
  *
  * @param {Object} object (constructed Assertion)
  * @param {Arguments} chai.Assertion.prototype.assert arguments
  * @namespace Utils
  * @name getOperator
  * @api public
  */
 
 module.exports = function getOperator(obj, args) {
   var operator = flag(obj, 'operator');
   var negate = flag(obj, 'negate');
   var expected = args[3];
   var msg = negate ? args[2] : args[1];
 
   if (operator) {
     return operator;
   }
 
   if (typeof msg === 'function') msg = msg();
 
   msg = msg || '';
   if (!msg) {
     return undefined;
   }
 
   if (/\shave\s/.test(msg)) {
     return undefined;
   }
 
   var isObject = isObjectType(expected);
   if (/\snot\s/.test(msg)) {
     return isObject ? 'notDeepStrictEqual' : 'notStrictEqual';
   }
 
   return isObject ? 'deepStrictEqual' : 'strictEqual';
 };
 
 },{"./flag":15,"type-detect":39}],20:[function(require,module,exports){
 /*!
  * Chai - getOwnEnumerableProperties utility
  * Copyright(c) 2011-2016 Jake Luer <jake@alogicalparadox.com>
  * MIT Licensed
  */
 
 /*!
  * Module dependencies
  */
 
 var getOwnEnumerablePropertySymbols = require('./getOwnEnumerablePropertySymbols');
 
 /**
  * ### .getOwnEnumerableProperties(object)
  *
  * This allows the retrieval of directly-owned enumerable property names and
  * symbols of an object. This function is necessary because Object.keys only
  * returns enumerable property names, not enumerable property symbols.
  *
  * @param {Object} object
  * @returns {Array}
  * @namespace Utils
  * @name getOwnEnumerableProperties
  * @api public
  */
 
 module.exports = function getOwnEnumerableProperties(obj) {
   return Object.keys(obj).concat(getOwnEnumerablePropertySymbols(obj));
 };
 
 },{"./getOwnEnumerablePropertySymbols":21}],21:[function(require,module,exports){
 /*!
  * Chai - getOwnEnumerablePropertySymbols utility
  * Copyright(c) 2011-2016 Jake Luer <jake@alogicalparadox.com>
  * MIT Licensed
  */
 
 /**
  * ### .getOwnEnumerablePropertySymbols(object)
  *
  * This allows the retrieval of directly-owned enumerable property symbols of an
  * object. This function is necessary because Object.getOwnPropertySymbols
  * returns both enumerable and non-enumerable property symbols.
  *
  * @param {Object} object
  * @returns {Array}
  * @namespace Utils
  * @name getOwnEnumerablePropertySymbols
  * @api public
  */
 
 module.exports = function getOwnEnumerablePropertySymbols(obj) {
   if (typeof Object.getOwnPropertySymbols !== 'function') return [];
 
   return Object.getOwnPropertySymbols(obj).filter(function (sym) {
     return Object.getOwnPropertyDescriptor(obj, sym).enumerable;
   });
 };
 
 },{}],22:[function(require,module,exports){
 /*!
  * Chai - getProperties utility
  * Copyright(c) 2012-2014 Jake Luer <jake@alogicalparadox.com>
  * MIT Licensed
  */
 
 /**
  * ### .getProperties(object)
  *
  * This allows the retrieval of property names of an object, enumerable or not,
  * inherited or not.
  *
  * @param {Object} object
  * @returns {Array}
  * @namespace Utils
  * @name getProperties
  * @api public
  */
 
 module.exports = function getProperties(object) {
   var result = Object.getOwnPropertyNames(object);
 
   function addProperty(property) {
     if (result.indexOf(property) === -1) {
       result.push(property);
     }
   }
 
   var proto = Object.getPrototypeOf(object);
   while (proto !== null) {
     Object.getOwnPropertyNames(proto).forEach(addProperty);
     proto = Object.getPrototypeOf(proto);
   }
 
   return result;
 };
 
 },{}],23:[function(require,module,exports){
 /*!
  * chai
  * Copyright(c) 2011 Jake Luer <jake@alogicalparadox.com>
  * MIT Licensed
  */
 
 /*!
  * Dependencies that are used for multiple exports are required here only once
  */
 
 var pathval = require('pathval');
 
 /*!
  * test utility
  */
 
 exports.test = require('./test');
 
 /*!
  * type utility
  */
 
 exports.type = require('type-detect');
 
 /*!
  * expectTypes utility
  */
 exports.expectTypes = require('./expectTypes');
 
 /*!
  * message utility
  */
 
 exports.getMessage = require('./getMessage');
 
 /*!
  * actual utility
  */
 
 exports.getActual = require('./getActual');
 
 /*!
  * Inspect util
  */
 
 exports.inspect = require('./inspect');
 
 /*!
  * Object Display util
  */
 
 exports.objDisplay = require('./objDisplay');
 
 /*!
  * Flag utility
  */
 
 exports.flag = require('./flag');
 
 /*!
  * Flag transferring utility
  */
 
 exports.transferFlags = require('./transferFlags');
 
 /*!
  * Deep equal utility
  */
 
 exports.eql = require('deep-eql');
 
 /*!
  * Deep path info
  */
 
 exports.getPathInfo = pathval.getPathInfo;
 
 /*!
  * Check if a property exists
  */
 
 exports.hasProperty = pathval.hasProperty;
 
 /*!
  * Function name
  */
 
 exports.getName = require('get-func-name');
 
 /*!
  * add Property
  */
 
 exports.addProperty = require('./addProperty');
 
 /*!
  * add Method
  */
 
 exports.addMethod = require('./addMethod');
 
 /*!
  * overwrite Property
  */
 
 exports.overwriteProperty = require('./overwriteProperty');
 
 /*!
  * overwrite Method
  */
 
 exports.overwriteMethod = require('./overwriteMethod');
 
 /*!
  * Add a chainable method
  */
 
 exports.addChainableMethod = require('./addChainableMethod');
 
 /*!
  * Overwrite chainable method
  */
 
 exports.overwriteChainableMethod = require('./overwriteChainableMethod');
 
 /*!
  * Compare by inspect method
  */
 
 exports.compareByInspect = require('./compareByInspect');
 
 /*!
  * Get own enumerable property symbols method
  */
 
 exports.getOwnEnumerablePropertySymbols = require('./getOwnEnumerablePropertySymbols');
 
 /*!
  * Get own enumerable properties method
  */
 
 exports.getOwnEnumerableProperties = require('./getOwnEnumerableProperties');
 
 /*!
  * Checks error against a given set of criteria
  */
 
 exports.checkError = require('check-error');
 
 /*!
  * Proxify util
  */
 
 exports.proxify = require('./proxify');
 
 /*!
  * addLengthGuard util
  */
 
 exports.addLengthGuard = require('./addLengthGuard');
 
 /*!
  * isProxyEnabled helper
  */
 
 exports.isProxyEnabled = require('./isProxyEnabled');
 
 /*!
  * isNaN method
  */
 
 exports.isNaN = require('./isNaN');
 
 /*!
  * getOperator method
  */
 
 exports.getOperator = require('./getOperator');
 },{"./addChainableMethod":9,"./addLengthGuard":10,"./addMethod":11,"./addProperty":12,"./compareByInspect":13,"./expectTypes":14,"./flag":15,"./getActual":16,"./getMessage":18,"./getOperator":19,"./getOwnEnumerableProperties":20,"./getOwnEnumerablePropertySymbols":21,"./inspect":24,"./isNaN":25,"./isProxyEnabled":26,"./objDisplay":27,"./overwriteChainableMethod":28,"./overwriteMethod":29,"./overwriteProperty":30,"./proxify":31,"./test":32,"./transferFlags":33,"check-error":35,"deep-eql":36,"get-func-name":37,"pathval":38,"type-detect":39}],24:[function(require,module,exports){
 // This is (almost) directly from Node.js utils
 // https://github.com/joyent/node/blob/f8c335d0caf47f16d31413f89aa28eda3878e3aa/lib/util.js
 
 var getName = require('get-func-name');
 var getProperties = require('./getProperties');
 var getEnumerableProperties = require('./getEnumerableProperties');
 var config = require('../config');
 
 module.exports = inspect;
 
 /**
  * ### .inspect(obj, [showHidden], [depth], [colors])
  *
  * Echoes the value of a value. Tries to print the value out
  * in the best way possible given the different types.
  *
  * @param {Object} obj The object to print out.
  * @param {Boolean} showHidden Flag that shows hidden (not enumerable)
  *    properties of objects. Default is false.
  * @param {Number} depth Depth in which to descend in object. Default is 2.
  * @param {Boolean} colors Flag to turn on ANSI escape codes to color the
  *    output. Default is false (no coloring).
  * @namespace Utils
  * @name inspect
  */
 function inspect(obj, showHidden, depth, colors) {
   var ctx = {
     showHidden: showHidden,
     seen: [],
     stylize: function (str) { return str; }
   };
   return formatValue(ctx, obj, (typeof depth === 'undefined' ? 2 : depth));
 }
 
 // Returns true if object is a DOM element.
 var isDOMElement = function (object) {
   if (typeof HTMLElement === 'object') {
     return object instanceof HTMLElement;
   } else {
     return object &&
       typeof object === 'object' &&
       'nodeType' in object &&
       object.nodeType === 1 &&
       typeof object.nodeName === 'string';
   }
 };
 
 function formatValue(ctx, value, recurseTimes) {
   // Provide a hook for user-specified inspect functions.
   // Check that value is an object with an inspect function on it
   if (value && typeof value.inspect === 'function' &&
       // Filter out the util module, it's inspect function is special
       value.inspect !== exports.inspect &&
       // Also filter out any prototype objects using the circular check.
       !(value.constructor && value.constructor.prototype === value)) {
     var ret = value.inspect(recurseTimes, ctx);
     if (typeof ret !== 'string') {
       ret = formatValue(ctx, ret, recurseTimes);
     }
     return ret;
   }
 
   // Primitive types cannot have properties
   var primitive = formatPrimitive(ctx, value);
   if (primitive) {
     return primitive;
   }
 
   // If this is a DOM element, try to get the outer HTML.
   if (isDOMElement(value)) {
     if ('outerHTML' in value) {
       return value.outerHTML;
       // This value does not have an outerHTML attribute,
       //   it could still be an XML element
     } else {
       // Attempt to serialize it
       try {
         if (document.xmlVersion) {
           var xmlSerializer = new XMLSerializer();
           return xmlSerializer.serializeToString(value);
         } else {
           // Firefox 11- do not support outerHTML
           //   It does, however, support innerHTML
           //   Use the following to render the element
           var ns = "http://www.w3.org/1999/xhtml";
           var container = document.createElementNS(ns, '_');
 
           container.appendChild(value.cloneNode(false));
           var html = container.innerHTML
             .replace('><', '>' + value.innerHTML + '<');
           container.innerHTML = '';
           return html;
         }
       } catch (err) {
         // This could be a non-native DOM implementation,
         //   continue with the normal flow:
         //   printing the element as if it is an object.
       }
     }
   }
 
   // Look up the keys of the object.
   var visibleKeys = getEnumerableProperties(value);
   var keys = ctx.showHidden ? getProperties(value) : visibleKeys;
 
   var name, nameSuffix;
 
   // Some type of object without properties can be shortcut.
   // In IE, errors have a single `stack` property, or if they are vanilla `Error`,
   // a `stack` plus `description` property; ignore those for consistency.
   if (keys.length === 0 || (isError(value) && (
       (keys.length === 1 && keys[0] === 'stack') ||
       (keys.length === 2 && keys[0] === 'description' && keys[1] === 'stack')
      ))) {
     if (typeof value === 'function') {
       name = getName(value);
       nameSuffix = name ? ': ' + name : '';
       return ctx.stylize('[Function' + nameSuffix + ']', 'special');
     }
     if (isRegExp(value)) {
       return ctx.stylize(RegExp.prototype.toString.call(value), 'regexp');
     }
     if (isDate(value)) {
       return ctx.stylize(Date.prototype.toUTCString.call(value), 'date');
     }
     if (isError(value)) {
       return formatError(value);
     }
   }
 
   var base = ''
     , array = false
     , typedArray = false
     , braces = ['{', '}'];
 
   if (isTypedArray(value)) {
     typedArray = true;
     braces = ['[', ']'];
   }
 
   // Make Array say that they are Array
   if (isArray(value)) {
     array = true;
     braces = ['[', ']'];
   }
 
   // Make functions say that they are functions
   if (typeof value === 'function') {
     name = getName(value);
     nameSuffix = name ? ': ' + name : '';
     base = ' [Function' + nameSuffix + ']';
   }
 
   // Make RegExps say that they are RegExps
   if (isRegExp(value)) {
     base = ' ' + RegExp.prototype.toString.call(value);
   }
 
   // Make dates with properties first say the date
   if (isDate(value)) {
     base = ' ' + Date.prototype.toUTCString.call(value);
   }
 
   // Make error with message first say the error
   if (isError(value)) {
     return formatError(value);
   }
 
   if (keys.length === 0 && (!array || value.length == 0)) {
     return braces[0] + base + braces[1];
   }
 
   if (recurseTimes < 0) {
     if (isRegExp(value)) {
       return ctx.stylize(RegExp.prototype.toString.call(value), 'regexp');
     } else {
       return ctx.stylize('[Object]', 'special');
     }
   }
 
   ctx.seen.push(value);
 
   var output;
   if (array) {
     output = formatArray(ctx, value, recurseTimes, visibleKeys, keys);
   } else if (typedArray) {
     return formatTypedArray(value);
   } else {
     output = keys.map(function(key) {
       return formatProperty(ctx, value, recurseTimes, visibleKeys, key, array);
     });
   }
 
   ctx.seen.pop();
 
   return reduceToSingleString(output, base, braces);
 }
 
 function formatPrimitive(ctx, value) {
   switch (typeof value) {
     case 'undefined':
       return ctx.stylize('undefined', 'undefined');
 
     case 'string':
       var simple = '\'' + JSON.stringify(value).replace(/^"|"$/g, '')
                                                .replace(/'/g, "\\'")
                                                .replace(/\\"/g, '"') + '\'';
       return ctx.stylize(simple, 'string');
 
     case 'number':
       if (value === 0 && (1/value) === -Infinity) {
         return ctx.stylize('-0', 'number');
       }
       return ctx.stylize('' + value, 'number');
 
     case 'boolean':
       return ctx.stylize('' + value, 'boolean');
 
     case 'symbol':
       return ctx.stylize(value.toString(), 'symbol');
 
     case 'bigint':
       return ctx.stylize(value.toString() + 'n', 'bigint');
   }
   // For some reason typeof null is "object", so special case here.
   if (value === null) {
     return ctx.stylize('null', 'null');
   }
 }
 
 function formatError(value) {
   return '[' + Error.prototype.toString.call(value) + ']';
 }
 
 function formatArray(ctx, value, recurseTimes, visibleKeys, keys) {
   var output = [];
   for (var i = 0, l = value.length; i < l; ++i) {
     if (Object.prototype.hasOwnProperty.call(value, String(i))) {
       output.push(formatProperty(ctx, value, recurseTimes, visibleKeys,
           String(i), true));
     } else {
       output.push('');
     }
   }
 
   keys.forEach(function(key) {
     if (!key.match(/^\d+$/)) {
       output.push(formatProperty(ctx, value, recurseTimes, visibleKeys,
           key, true));
     }
   });
   return output;
 }
 
 function formatTypedArray(value) {
   var str = '[ ';
 
   for (var i = 0; i < value.length; ++i) {
     if (str.length >= config.truncateThreshold - 7) {
       str += '...';
       break;
     }
     str += value[i] + ', ';
   }
   str += ' ]';
 
   // Removing trailing `, ` if the array was not truncated
   if (str.indexOf(',  ]') !== -1) {
     str = str.replace(',  ]', ' ]');
   }
 
   return str;
 }
 
 function formatProperty(ctx, value, recurseTimes, visibleKeys, key, array) {
   var name;
   var propDescriptor = Object.getOwnPropertyDescriptor(value, key);
   var str;
 
   if (propDescriptor) {
     if (propDescriptor.get) {
       if (propDescriptor.set) {
         str = ctx.stylize('[Getter/Setter]', 'special');
       } else {
         str = ctx.stylize('[Getter]', 'special');
       }
     } else {
       if (propDescriptor.set) {
         str = ctx.stylize('[Setter]', 'special');
       }
     }
   }
   if (visibleKeys.indexOf(key) < 0) {
     name = '[' + key + ']';
   }
   if (!str) {
     if (ctx.seen.indexOf(value[key]) < 0) {
       if (recurseTimes === null) {
         str = formatValue(ctx, value[key], null);
       } else {
         str = formatValue(ctx, value[key], recurseTimes - 1);
       }
       if (str.indexOf('\n') > -1) {
         if (array) {
           str = str.split('\n').map(function(line) {
             return '  ' + line;
           }).join('\n').substr(2);
         } else {
           str = '\n' + str.split('\n').map(function(line) {
             return '   ' + line;
           }).join('\n');
         }
       }
     } else {
       str = ctx.stylize('[Circular]', 'special');
     }
   }
   if (typeof name === 'undefined') {
     if (array && key.match(/^\d+$/)) {
       return str;
     }
     name = JSON.stringify('' + key);
     if (name.match(/^"([a-zA-Z_][a-zA-Z_0-9]*)"$/)) {
       name = name.substr(1, name.length - 2);
       name = ctx.stylize(name, 'name');
     } else {
       name = name.replace(/'/g, "\\'")
                  .replace(/\\"/g, '"')
                  .replace(/(^"|"$)/g, "'");
       name = ctx.stylize(name, 'string');
     }
   }
 
   return name + ': ' + str;
 }
 
 function reduceToSingleString(output, base, braces) {
   var length = output.reduce(function(prev, cur) {
     return prev + cur.length + 1;
   }, 0);
 
   if (length > 60) {
     return braces[0] +
            (base === '' ? '' : base + '\n ') +
            ' ' +
            output.join(',\n  ') +
            ' ' +
            braces[1];
   }
 
   return braces[0] + base + ' ' + output.join(', ') + ' ' + braces[1];
 }
 
 function isTypedArray(ar) {
   // Unfortunately there's no way to check if an object is a TypedArray
   // We have to check if it's one of these types
   return (typeof ar === 'object' && /\w+Array]$/.test(objectToString(ar)));
 }
 
 function isArray(ar) {
   return Array.isArray(ar) ||
          (typeof ar === 'object' && objectToString(ar) === '[object Array]');
 }
 
 function isRegExp(re) {
   return typeof re === 'object' && objectToString(re) === '[object RegExp]';
 }
 
 function isDate(d) {
   return typeof d === 'object' && objectToString(d) === '[object Date]';
 }
 
 function isError(e) {
   return typeof e === 'object' && objectToString(e) === '[object Error]';
 }
 
 function objectToString(o) {
   return Object.prototype.toString.call(o);
 }
 
 },{"../config":4,"./getEnumerableProperties":17,"./getProperties":22,"get-func-name":37}],25:[function(require,module,exports){
 /*!
  * Chai - isNaN utility
  * Copyright(c) 2012-2015 Sakthipriyan Vairamani <thechargingvolcano@gmail.com>
  * MIT Licensed
  */
 
 /**
  * ### .isNaN(value)
  *
  * Checks if the given value is NaN or not.
  *
  *     utils.isNaN(NaN); // true
  *
  * @param {Value} The value which has to be checked if it is NaN
  * @name isNaN
  * @api private
  */
 
 function isNaN(value) {
   // Refer http://www.ecma-international.org/ecma-262/6.0/#sec-isnan-number
   // section's NOTE.
   return value !== value;
 }
 
 // If ECMAScript 6's Number.isNaN is present, prefer that.
 module.exports = Number.isNaN || isNaN;
 
 },{}],26:[function(require,module,exports){
 var config = require('../config');
 
 /*!
  * Chai - isProxyEnabled helper
  * Copyright(c) 2012-2014 Jake Luer <jake@alogicalparadox.com>
  * MIT Licensed
  */
 
 /**
  * ### .isProxyEnabled()
  *
  * Helper function to check if Chai's proxy protection feature is enabled. If
  * proxies are unsupported or disabled via the user's Chai config, then return
  * false. Otherwise, return true.
  *
  * @namespace Utils
  * @name isProxyEnabled
  */
 
 module.exports = function isProxyEnabled() {
   return config.useProxy &&
     typeof Proxy !== 'undefined' &&
     typeof Reflect !== 'undefined';
 };
 
 },{"../config":4}],27:[function(require,module,exports){
 /*!
  * Chai - flag utility
  * Copyright(c) 2012-2014 Jake Luer <jake@alogicalparadox.com>
  * MIT Licensed
  */
 
 /*!
  * Module dependencies
  */
 
 var inspect = require('./inspect');
 var config = require('../config');
 
 /**
  * ### .objDisplay(object)
  *
  * Determines if an object or an array matches
  * criteria to be inspected in-line for error
  * messages or should be truncated.
  *
  * @param {Mixed} javascript object to inspect
  * @name objDisplay
  * @namespace Utils
  * @api public
  */
 
 module.exports = function objDisplay(obj) {
   var str = inspect(obj)
     , type = Object.prototype.toString.call(obj);
 
   if (config.truncateThreshold && str.length >= config.truncateThreshold) {
     if (type === '[object Function]') {
       return !obj.name || obj.name === ''
         ? '[Function]'
         : '[Function: ' + obj.name + ']';
     } else if (type === '[object Array]') {
       return '[ Array(' + obj.length + ') ]';
     } else if (type === '[object Object]') {
       var keys = Object.keys(obj)
         , kstr = keys.length > 2
           ? keys.splice(0, 2).join(', ') + ', ...'
           : keys.join(', ');
       return '{ Object (' + kstr + ') }';
     } else {
       return str;
     }
   } else {
     return str;
   }
 };
 
 },{"../config":4,"./inspect":24}],28:[function(require,module,exports){
 /*!
  * Chai - overwriteChainableMethod utility
  * Copyright(c) 2012-2014 Jake Luer <jake@alogicalparadox.com>
  * MIT Licensed
  */
 
 var chai = require('../../chai');
 var transferFlags = require('./transferFlags');
 
 /**
  * ### .overwriteChainableMethod(ctx, name, method, chainingBehavior)
  *
  * Overwrites an already existing chainable method
  * and provides access to the previous function or
  * property.  Must return functions to be used for
  * name.
  *
  *     utils.overwriteChainableMethod(chai.Assertion.prototype, 'lengthOf',
  *       function (_super) {
  *       }
  *     , function (_super) {
  *       }
  *     );
  *
  * Can also be accessed directly from `chai.Assertion`.
  *
  *     chai.Assertion.overwriteChainableMethod('foo', fn, fn);
  *
  * Then can be used as any other assertion.
  *
  *     expect(myFoo).to.have.lengthOf(3);
  *     expect(myFoo).to.have.lengthOf.above(3);
  *
  * @param {Object} ctx object whose method / property is to be overwritten
  * @param {String} name of method / property to overwrite
  * @param {Function} method function that returns a function to be used for name
  * @param {Function} chainingBehavior function that returns a function to be used for property
  * @namespace Utils
  * @name overwriteChainableMethod
  * @api public
  */
 
 module.exports = function overwriteChainableMethod(ctx, name, method, chainingBehavior) {
   var chainableBehavior = ctx.__methods[name];
 
   var _chainingBehavior = chainableBehavior.chainingBehavior;
   chainableBehavior.chainingBehavior = function overwritingChainableMethodGetter() {
     var result = chainingBehavior(_chainingBehavior).call(this);
     if (result !== undefined) {
       return result;
     }
 
     var newAssertion = new chai.Assertion();
     transferFlags(this, newAssertion);
     return newAssertion;
   };
 
   var _method = chainableBehavior.method;
   chainableBehavior.method = function overwritingChainableMethodWrapper() {
     var result = method(_method).apply(this, arguments);
     if (result !== undefined) {
       return result;
     }
 
     var newAssertion = new chai.Assertion();
     transferFlags(this, newAssertion);
     return newAssertion;
   };
 };
 
 },{"../../chai":2,"./transferFlags":33}],29:[function(require,module,exports){
 /*!
  * Chai - overwriteMethod utility
  * Copyright(c) 2012-2014 Jake Luer <jake@alogicalparadox.com>
  * MIT Licensed
  */
 
 var addLengthGuard = require('./addLengthGuard');
 var chai = require('../../chai');
 var flag = require('./flag');
 var proxify = require('./proxify');
 var transferFlags = require('./transferFlags');
 
 /**
  * ### .overwriteMethod(ctx, name, fn)
  *
  * Overwrites an already existing method and provides
  * access to previous function. Must return function
  * to be used for name.
  *
  *     utils.overwriteMethod(chai.Assertion.prototype, 'equal', function (_super) {
  *       return function (str) {
  *         var obj = utils.flag(this, 'object');
  *         if (obj instanceof Foo) {
  *           new chai.Assertion(obj.value).to.equal(str);
  *         } else {
  *           _super.apply(this, arguments);
  *         }
  *       }
  *     });
  *
  * Can also be accessed directly from `chai.Assertion`.
  *
  *     chai.Assertion.overwriteMethod('foo', fn);
  *
  * Then can be used as any other assertion.
  *
  *     expect(myFoo).to.equal('bar');
  *
  * @param {Object} ctx object whose method is to be overwritten
  * @param {String} name of method to overwrite
  * @param {Function} method function that returns a function to be used for name
  * @namespace Utils
  * @name overwriteMethod
  * @api public
  */
 
 module.exports = function overwriteMethod(ctx, name, method) {
   var _method = ctx[name]
     , _super = function () {
       throw new Error(name + ' is not a function');
     };
 
   if (_method && 'function' === typeof _method)
     _super = _method;
 
   var overwritingMethodWrapper = function () {
     // Setting the `ssfi` flag to `overwritingMethodWrapper` causes this
     // function to be the starting point for removing implementation frames from
     // the stack trace of a failed assertion.
     //
     // However, we only want to use this function as the starting point if the
     // `lockSsfi` flag isn't set.
     //
     // If the `lockSsfi` flag is set, then either this assertion has been
     // overwritten by another assertion, or this assertion is being invoked from
     // inside of another assertion. In the first case, the `ssfi` flag has
     // already been set by the overwriting assertion. In the second case, the
     // `ssfi` flag has already been set by the outer assertion.
     if (!flag(this, 'lockSsfi')) {
       flag(this, 'ssfi', overwritingMethodWrapper);
     }
 
     // Setting the `lockSsfi` flag to `true` prevents the overwritten assertion
     // from changing the `ssfi` flag. By this point, the `ssfi` flag is already
     // set to the correct starting point for this assertion.
     var origLockSsfi = flag(this, 'lockSsfi');
     flag(this, 'lockSsfi', true);
     var result = method(_super).apply(this, arguments);
     flag(this, 'lockSsfi', origLockSsfi);
 
     if (result !== undefined) {
       return result;
     }
 
     var newAssertion = new chai.Assertion();
     transferFlags(this, newAssertion);
     return newAssertion;
   }
 
   addLengthGuard(overwritingMethodWrapper, name, false);
   ctx[name] = proxify(overwritingMethodWrapper, name);
 };
 
 },{"../../chai":2,"./addLengthGuard":10,"./flag":15,"./proxify":31,"./transferFlags":33}],30:[function(require,module,exports){
 /*!
  * Chai - overwriteProperty utility
  * Copyright(c) 2012-2014 Jake Luer <jake@alogicalparadox.com>
  * MIT Licensed
  */
 
 var chai = require('../../chai');
 var flag = require('./flag');
 var isProxyEnabled = require('./isProxyEnabled');
 var transferFlags = require('./transferFlags');
 
 /**
  * ### .overwriteProperty(ctx, name, fn)
  *
  * Overwrites an already existing property getter and provides
  * access to previous value. Must return function to use as getter.
  *
  *     utils.overwriteProperty(chai.Assertion.prototype, 'ok', function (_super) {
  *       return function () {
  *         var obj = utils.flag(this, 'object');
  *         if (obj instanceof Foo) {
  *           new chai.Assertion(obj.name).to.equal('bar');
  *         } else {
  *           _super.call(this);
  *         }
  *       }
  *     });
  *
  *
  * Can also be accessed directly from `chai.Assertion`.
  *
  *     chai.Assertion.overwriteProperty('foo', fn);
  *
  * Then can be used as any other assertion.
  *
  *     expect(myFoo).to.be.ok;
  *
  * @param {Object} ctx object whose property is to be overwritten
  * @param {String} name of property to overwrite
  * @param {Function} getter function that returns a getter function to be used for name
  * @namespace Utils
  * @name overwriteProperty
  * @api public
  */
 
 module.exports = function overwriteProperty(ctx, name, getter) {
   var _get = Object.getOwnPropertyDescriptor(ctx, name)
     , _super = function () {};
 
   if (_get && 'function' === typeof _get.get)
     _super = _get.get
 
   Object.defineProperty(ctx, name,
     { get: function overwritingPropertyGetter() {
         // Setting the `ssfi` flag to `overwritingPropertyGetter` causes this
         // function to be the starting point for removing implementation frames
         // from the stack trace of a failed assertion.
         //
         // However, we only want to use this function as the starting point if
         // the `lockSsfi` flag isn't set and proxy protection is disabled.
         //
         // If the `lockSsfi` flag is set, then either this assertion has been
         // overwritten by another assertion, or this assertion is being invoked
         // from inside of another assertion. In the first case, the `ssfi` flag
         // has already been set by the overwriting assertion. In the second
         // case, the `ssfi` flag has already been set by the outer assertion.
         //
         // If proxy protection is enabled, then the `ssfi` flag has already been
         // set by the proxy getter.
         if (!isProxyEnabled() && !flag(this, 'lockSsfi')) {
           flag(this, 'ssfi', overwritingPropertyGetter);
         }
 
         // Setting the `lockSsfi` flag to `true` prevents the overwritten
         // assertion from changing the `ssfi` flag. By this point, the `ssfi`
         // flag is already set to the correct starting point for this assertion.
         var origLockSsfi = flag(this, 'lockSsfi');
         flag(this, 'lockSsfi', true);
         var result = getter(_super).call(this);
         flag(this, 'lockSsfi', origLockSsfi);
 
         if (result !== undefined) {
           return result;
         }
 
         var newAssertion = new chai.Assertion();
         transferFlags(this, newAssertion);
         return newAssertion;
       }
     , configurable: true
   });
 };
 
 },{"../../chai":2,"./flag":15,"./isProxyEnabled":26,"./transferFlags":33}],31:[function(require,module,exports){
 var config = require('../config');
 var flag = require('./flag');
 var getProperties = require('./getProperties');
 var isProxyEnabled = require('./isProxyEnabled');
 
 /*!
  * Chai - proxify utility
  * Copyright(c) 2012-2014 Jake Luer <jake@alogicalparadox.com>
  * MIT Licensed
  */
 
 /**
  * ### .proxify(object)
  *
  * Return a proxy of given object that throws an error when a non-existent
  * property is read. By default, the root cause is assumed to be a misspelled
  * property, and thus an attempt is made to offer a reasonable suggestion from
  * the list of existing properties. However, if a nonChainableMethodName is
  * provided, then the root cause is instead a failure to invoke a non-chainable
  * method prior to reading the non-existent property.
  *
  * If proxies are unsupported or disabled via the user's Chai config, then
  * return object without modification.
  *
  * @param {Object} obj
  * @param {String} nonChainableMethodName
  * @namespace Utils
  * @name proxify
  */
 
 var builtins = ['__flags', '__methods', '_obj', 'assert'];
 
 module.exports = function proxify(obj, nonChainableMethodName) {
   if (!isProxyEnabled()) return obj;
 
   return new Proxy(obj, {
     get: function proxyGetter(target, property) {
       // This check is here because we should not throw errors on Symbol properties
       // such as `Symbol.toStringTag`.
       // The values for which an error should be thrown can be configured using
       // the `config.proxyExcludedKeys` setting.
       if (typeof property === 'string' &&
           config.proxyExcludedKeys.indexOf(property) === -1 &&
           !Reflect.has(target, property)) {
         // Special message for invalid property access of non-chainable methods.
         if (nonChainableMethodName) {
           throw Error('Invalid Chai property: ' + nonChainableMethodName + '.' +
             property + '. See docs for proper usage of "' +
             nonChainableMethodName + '".');
         }
 
         // If the property is reasonably close to an existing Chai property,
         // suggest that property to the user. Only suggest properties with a
         // distance less than 4.
         var suggestion = null;
         var suggestionDistance = 4;
         getProperties(target).forEach(function(prop) {
           if (
             !Object.prototype.hasOwnProperty(prop) &&
             builtins.indexOf(prop) === -1
           ) {
             var dist = stringDistanceCapped(
               property,
               prop,
               suggestionDistance
             );
             if (dist < suggestionDistance) {
               suggestion = prop;
               suggestionDistance = dist;
             }
           }
         });
 
         if (suggestion !== null) {
           throw Error('Invalid Chai property: ' + property +
             '. Did you mean "' + suggestion + '"?');
         } else {
           throw Error('Invalid Chai property: ' + property);
         }
       }
 
       // Use this proxy getter as the starting point for removing implementation
       // frames from the stack trace of a failed assertion. For property
       // assertions, this prevents the proxy getter from showing up in the stack
       // trace since it's invoked before the property getter. For method and
       // chainable method assertions, this flag will end up getting changed to
       // the method wrapper, which is good since this frame will no longer be in
       // the stack once the method is invoked. Note that Chai builtin assertion
       // properties such as `__flags` are skipped since this is only meant to
       // capture the starting point of an assertion. This step is also skipped
       // if the `lockSsfi` flag is set, thus indicating that this assertion is
       // being called from within another assertion. In that case, the `ssfi`
       // flag is already set to the outer assertion's starting point.
       if (builtins.indexOf(property) === -1 && !flag(target, 'lockSsfi')) {
         flag(target, 'ssfi', proxyGetter);
       }
 
       return Reflect.get(target, property);
     }
   });
 };
 
 /**
  * # stringDistanceCapped(strA, strB, cap)
  * Return the Levenshtein distance between two strings, but no more than cap.
  * @param {string} strA
  * @param {string} strB
  * @param {number} number
  * @return {number} min(string distance between strA and strB, cap)
  * @api private
  */
 
 function stringDistanceCapped(strA, strB, cap) {
   if (Math.abs(strA.length - strB.length) >= cap) {
     return cap;
   }
 
   var memo = [];
   // `memo` is a two-dimensional array containing distances.
   // memo[i][j] is the distance between strA.slice(0, i) and
   // strB.slice(0, j).
   for (var i = 0; i <= strA.length; i++) {
     memo[i] = Array(strB.length + 1).fill(0);
     memo[i][0] = i;
   }
   for (var j = 0; j < strB.length; j++) {
     memo[0][j] = j;
   }
 
   for (var i = 1; i <= strA.length; i++) {
     var ch = strA.charCodeAt(i - 1);
     for (var j = 1; j <= strB.length; j++) {
       if (Math.abs(i - j) >= cap) {
         memo[i][j] = cap;
         continue;
       }
       memo[i][j] = Math.min(
         memo[i - 1][j] + 1,
         memo[i][j - 1] + 1,
         memo[i - 1][j - 1] +
           (ch === strB.charCodeAt(j - 1) ? 0 : 1)
       );
     }
   }
 
   return memo[strA.length][strB.length];
 }
 
 },{"../config":4,"./flag":15,"./getProperties":22,"./isProxyEnabled":26}],32:[function(require,module,exports){
 /*!
  * Chai - test utility
  * Copyright(c) 2012-2014 Jake Luer <jake@alogicalparadox.com>
  * MIT Licensed
  */
 
 /*!
  * Module dependencies
  */
 
 var flag = require('./flag');
 
 /**
  * ### .test(object, expression)
  *
  * Test and object for expression.
  *
  * @param {Object} object (constructed Assertion)
  * @param {Arguments} chai.Assertion.prototype.assert arguments
  * @namespace Utils
  * @name test
  */
 
 module.exports = function test(obj, args) {
   var negate = flag(obj, 'negate')
     , expr = args[0];
   return negate ? !expr : expr;
 };
 
 },{"./flag":15}],33:[function(require,module,exports){
 /*!
  * Chai - transferFlags utility
  * Copyright(c) 2012-2014 Jake Luer <jake@alogicalparadox.com>
  * MIT Licensed
  */
 
 /**
  * ### .transferFlags(assertion, object, includeAll = true)
  *
  * Transfer all the flags for `assertion` to `object`. If
  * `includeAll` is set to `false`, then the base Chai
  * assertion flags (namely `object`, `ssfi`, `lockSsfi`,
  * and `message`) will not be transferred.
  *
  *
  *     var newAssertion = new Assertion();
  *     utils.transferFlags(assertion, newAssertion);
  *
  *     var anotherAssertion = new Assertion(myObj);
  *     utils.transferFlags(assertion, anotherAssertion, false);
  *
  * @param {Assertion} assertion the assertion to transfer the flags from
  * @param {Object} object the object to transfer the flags to; usually a new assertion
  * @param {Boolean} includeAll
  * @namespace Utils
  * @name transferFlags
  * @api private
  */
 
 module.exports = function transferFlags(assertion, object, includeAll) {
   var flags = assertion.__flags || (assertion.__flags = Object.create(null));
 
   if (!object.__flags) {
     object.__flags = Object.create(null);
   }
 
   includeAll = arguments.length === 3 ? includeAll : true;
 
   for (var flag in flags) {
     if (includeAll ||
         (flag !== 'object' && flag !== 'ssfi' && flag !== 'lockSsfi' && flag != 'message')) {
       object.__flags[flag] = flags[flag];
     }
   }
 };
 
 },{}],34:[function(require,module,exports){
 /*!
  * assertion-error
  * Copyright(c) 2013 Jake Luer <jake@qualiancy.com>
  * MIT Licensed
  */
 
 /*!
  * Return a function that will copy properties from
  * one object to another excluding any originally
  * listed. Returned function will create a new `{}`.
  *
  * @param {String} excluded properties ...
  * @return {Function}
  */
 
 function exclude () {
   var excludes = [].slice.call(arguments);
 
   function excludeProps (res, obj) {
     Object.keys(obj).forEach(function (key) {
       if (!~excludes.indexOf(key)) res[key] = obj[key];
     });
   }
 
   return function extendExclude () {
     var args = [].slice.call(arguments)
       , i = 0
       , res = {};
 
     for (; i < args.length; i++) {
       excludeProps(res, args[i]);
     }
 
     return res;
   };
 };
 
 /*!
  * Primary Exports
  */
 
 module.exports = AssertionError;
 
 /**
  * ### AssertionError
  *
  * An extension of the JavaScript `Error` constructor for
  * assertion and validation scenarios.
  *
  * @param {String} message
  * @param {Object} properties to include (optional)
  * @param {callee} start stack function (optional)
  */
 
 function AssertionError (message, _props, ssf) {
   var extend = exclude('name', 'message', 'stack', 'constructor', 'toJSON')
     , props = extend(_props || {});
 
   // default values
   this.message = message || 'Unspecified AssertionError';
   this.showDiff = false;
 
   // copy from properties
   for (var key in props) {
     this[key] = props[key];
   }
 
   // capture stack trace
   ssf = ssf || AssertionError;
   if (Error.captureStackTrace) {
     Error.captureStackTrace(this, ssf);
   } else {
     try {
       throw new Error();
     } catch(e) {
       this.stack = e.stack;
     }
   }
 }
 
 /*!
  * Inherit from Error.prototype
  */
 
 AssertionError.prototype = Object.create(Error.prototype);
 
 /*!
  * Statically set name
  */
 
 AssertionError.prototype.name = 'AssertionError';
 
 /*!
  * Ensure correct constructor
  */
 
 AssertionError.prototype.constructor = AssertionError;
 
 /**
  * Allow errors to be converted to JSON for static transfer.
  *
  * @param {Boolean} include stack (default: `true`)
  * @return {Object} object that can be `JSON.stringify`
  */
 
 AssertionError.prototype.toJSON = function (stack) {
   var extend = exclude('constructor', 'toJSON', 'stack')
     , props = extend({ name: this.name }, this);
 
   // include stack if exists and not turned off
   if (false !== stack && this.stack) {
     props.stack = this.stack;
   }
 
   return props;
 };
 
 },{}],35:[function(require,module,exports){
 'use strict';
 
 /* !
  * Chai - checkError utility
  * Copyright(c) 2012-2016 Jake Luer <jake@alogicalparadox.com>
  * MIT Licensed
  */
 
 /**
  * ### .checkError
  *
  * Checks that an error conforms to a given set of criteria and/or retrieves information about it.
  *
  * @api public
  */
 
 /**
  * ### .compatibleInstance(thrown, errorLike)
  *
  * Checks if two instances are compatible (strict equal).
  * Returns false if errorLike is not an instance of Error, because instances
  * can only be compatible if they're both error instances.
  *
  * @name compatibleInstance
  * @param {Error} thrown error
  * @param {Error|ErrorConstructor} errorLike object to compare against
  * @namespace Utils
  * @api public
  */
 
 function compatibleInstance(thrown, errorLike) {
   return errorLike instanceof Error && thrown === errorLike;
 }
 
 /**
  * ### .compatibleConstructor(thrown, errorLike)
  *
  * Checks if two constructors are compatible.
  * This function can receive either an error constructor or
  * an error instance as the `errorLike` argument.
  * Constructors are compatible if they're the same or if one is
  * an instance of another.
  *
  * @name compatibleConstructor
  * @param {Error} thrown error
  * @param {Error|ErrorConstructor} errorLike object to compare against
  * @namespace Utils
  * @api public
  */
 
 function compatibleConstructor(thrown, errorLike) {
   if (errorLike instanceof Error) {
     // If `errorLike` is an instance of any error we compare their constructors
     return thrown.constructor === errorLike.constructor || thrown instanceof errorLike.constructor;
   } else if (errorLike.prototype instanceof Error || errorLike === Error) {
     // If `errorLike` is a constructor that inherits from Error, we compare `thrown` to `errorLike` directly
     return thrown.constructor === errorLike || thrown instanceof errorLike;
   }
 
   return false;
 }
 
 /**
  * ### .compatibleMessage(thrown, errMatcher)
  *
  * Checks if an error's message is compatible with a matcher (String or RegExp).
  * If the message contains the String or passes the RegExp test,
  * it is considered compatible.
  *
  * @name compatibleMessage
  * @param {Error} thrown error
  * @param {String|RegExp} errMatcher to look for into the message
  * @namespace Utils
  * @api public
  */
 
 function compatibleMessage(thrown, errMatcher) {
   var comparisonString = typeof thrown === 'string' ? thrown : thrown.message;
   if (errMatcher instanceof RegExp) {
     return errMatcher.test(comparisonString);
   } else if (typeof errMatcher === 'string') {
     return comparisonString.indexOf(errMatcher) !== -1; // eslint-disable-line no-magic-numbers
   }
 
   return false;
 }
 
 /**
  * ### .getFunctionName(constructorFn)
  *
  * Returns the name of a function.
  * This also includes a polyfill function if `constructorFn.name` is not defined.
  *
  * @name getFunctionName
  * @param {Function} constructorFn
  * @namespace Utils
  * @api private
  */
 
 var functionNameMatch = /\s*function(?:\s|\s*\/\*[^(?:*\/)]+\*\/\s*)*([^\(\/]+)/;
 function getFunctionName(constructorFn) {
   var name = '';
   if (typeof constructorFn.name === 'undefined') {
     // Here we run a polyfill if constructorFn.name is not defined
     var match = String(constructorFn).match(functionNameMatch);
     if (match) {
       name = match[1];
     }
   } else {
     name = constructorFn.name;
   }
 
   return name;
 }
 
 /**
  * ### .getConstructorName(errorLike)
  *
  * Gets the constructor name for an Error instance or constructor itself.
  *
  * @name getConstructorName
  * @param {Error|ErrorConstructor} errorLike
  * @namespace Utils
  * @api public
  */
 
 function getConstructorName(errorLike) {
   var constructorName = errorLike;
   if (errorLike instanceof Error) {
     constructorName = getFunctionName(errorLike.constructor);
   } else if (typeof errorLike === 'function') {
     // If `err` is not an instance of Error it is an error constructor itself or another function.
     // If we've got a common function we get its name, otherwise we may need to create a new instance
     // of the error just in case it's a poorly-constructed error. Please see chaijs/chai/issues/45 to know more.
     constructorName = getFunctionName(errorLike).trim() ||
         getFunctionName(new errorLike()); // eslint-disable-line new-cap
   }
 
   return constructorName;
 }
 
 /**
  * ### .getMessage(errorLike)
  *
  * Gets the error message from an error.
  * If `err` is a String itself, we return it.
  * If the error has no message, we return an empty string.
  *
  * @name getMessage
  * @param {Error|String} errorLike
  * @namespace Utils
  * @api public
  */
 
 function getMessage(errorLike) {
   var msg = '';
   if (errorLike && errorLike.message) {
     msg = errorLike.message;
   } else if (typeof errorLike === 'string') {
     msg = errorLike;
   }
 
   return msg;
 }
 
 module.exports = {
   compatibleInstance: compatibleInstance,
   compatibleConstructor: compatibleConstructor,
   compatibleMessage: compatibleMessage,
   getMessage: getMessage,
   getConstructorName: getConstructorName,
 };
 
 },{}],36:[function(require,module,exports){
 'use strict';
 /* globals Symbol: false, Uint8Array: false, WeakMap: false */
 /*!
  * deep-eql
  * Copyright(c) 2013 Jake Luer <jake@alogicalparadox.com>
  * MIT Licensed
  */
 
 var type = require('type-detect');
 function FakeMap() {
   this._key = 'chai/deep-eql__' + Math.random() + Date.now();
 }
 
 FakeMap.prototype = {
   get: function getMap(key) {
     return key[this._key];
   },
   set: function setMap(key, value) {
     if (Object.isExtensible(key)) {
       Object.defineProperty(key, this._key, {
         value: value,
         configurable: true,
       });
     }
   },
 };
 
 var MemoizeMap = typeof WeakMap === 'function' ? WeakMap : FakeMap;
 /*!
  * Check to see if the MemoizeMap has recorded a result of the two operands
  *
  * @param {Mixed} leftHandOperand
  * @param {Mixed} rightHandOperand
  * @param {MemoizeMap} memoizeMap
  * @returns {Boolean|null} result
 */
 function memoizeCompare(leftHandOperand, rightHandOperand, memoizeMap) {
   // Technically, WeakMap keys can *only* be objects, not primitives.
   if (!memoizeMap || isPrimitive(leftHandOperand) || isPrimitive(rightHandOperand)) {
     return null;
   }
   var leftHandMap = memoizeMap.get(leftHandOperand);
   if (leftHandMap) {
     var result = leftHandMap.get(rightHandOperand);
     if (typeof result === 'boolean') {
       return result;
     }
   }
   return null;
 }
 
 /*!
  * Set the result of the equality into the MemoizeMap
  *
  * @param {Mixed} leftHandOperand
  * @param {Mixed} rightHandOperand
  * @param {MemoizeMap} memoizeMap
  * @param {Boolean} result
 */
 function memoizeSet(leftHandOperand, rightHandOperand, memoizeMap, result) {
   // Technically, WeakMap keys can *only* be objects, not primitives.
   if (!memoizeMap || isPrimitive(leftHandOperand) || isPrimitive(rightHandOperand)) {
     return;
   }
   var leftHandMap = memoizeMap.get(leftHandOperand);
   if (leftHandMap) {
     leftHandMap.set(rightHandOperand, result);
   } else {
     leftHandMap = new MemoizeMap();
     leftHandMap.set(rightHandOperand, result);
     memoizeMap.set(leftHandOperand, leftHandMap);
   }
 }
 
 /*!
  * Primary Export
  */
 
 module.exports = deepEqual;
 module.exports.MemoizeMap = MemoizeMap;
 
 /**
  * Assert deeply nested sameValue equality between two objects of any type.
  *
  * @param {Mixed} leftHandOperand
  * @param {Mixed} rightHandOperand
  * @param {Object} [options] (optional) Additional options
  * @param {Array} [options.comparator] (optional) Override default algorithm, determining custom equality.
  * @param {Array} [options.memoize] (optional) Provide a custom memoization object which will cache the results of
     complex objects for a speed boost. By passing `false` you can disable memoization, but this will cause circular
     references to blow the stack.
  * @return {Boolean} equal match
  */
 function deepEqual(leftHandOperand, rightHandOperand, options) {
   // If we have a comparator, we can't assume anything; so bail to its check first.
   if (options && options.comparator) {
     return extensiveDeepEqual(leftHandOperand, rightHandOperand, options);
   }
 
   var simpleResult = simpleEqual(leftHandOperand, rightHandOperand);
   if (simpleResult !== null) {
     return simpleResult;
   }
 
   // Deeper comparisons are pushed through to a larger function
   return extensiveDeepEqual(leftHandOperand, rightHandOperand, options);
 }
 
 /**
  * Many comparisons can be canceled out early via simple equality or primitive checks.
  * @param {Mixed} leftHandOperand
  * @param {Mixed} rightHandOperand
  * @return {Boolean|null} equal match
  */
 function simpleEqual(leftHandOperand, rightHandOperand) {
   // Equal references (except for Numbers) can be returned early
   if (leftHandOperand === rightHandOperand) {
     // Handle +-0 cases
     return leftHandOperand !== 0 || 1 / leftHandOperand === 1 / rightHandOperand;
   }
 
   // handle NaN cases
   if (
     leftHandOperand !== leftHandOperand && // eslint-disable-line no-self-compare
     rightHandOperand !== rightHandOperand // eslint-disable-line no-self-compare
   ) {
     return true;
   }
 
   // Anything that is not an 'object', i.e. symbols, functions, booleans, numbers,
   // strings, and undefined, can be compared by reference.
   if (isPrimitive(leftHandOperand) || isPrimitive(rightHandOperand)) {
     // Easy out b/c it would have passed the first equality check
     return false;
   }
   return null;
 }
 
 /*!
  * The main logic of the `deepEqual` function.
  *
  * @param {Mixed} leftHandOperand
  * @param {Mixed} rightHandOperand
  * @param {Object} [options] (optional) Additional options
  * @param {Array} [options.comparator] (optional) Override default algorithm, determining custom equality.
  * @param {Array} [options.memoize] (optional) Provide a custom memoization object which will cache the results of
     complex objects for a speed boost. By passing `false` you can disable memoization, but this will cause circular
     references to blow the stack.
  * @return {Boolean} equal match
 */
 function extensiveDeepEqual(leftHandOperand, rightHandOperand, options) {
   options = options || {};
   options.memoize = options.memoize === false ? false : options.memoize || new MemoizeMap();
   var comparator = options && options.comparator;
 
   // Check if a memoized result exists.
   var memoizeResultLeft = memoizeCompare(leftHandOperand, rightHandOperand, options.memoize);
   if (memoizeResultLeft !== null) {
     return memoizeResultLeft;
   }
   var memoizeResultRight = memoizeCompare(rightHandOperand, leftHandOperand, options.memoize);
   if (memoizeResultRight !== null) {
     return memoizeResultRight;
   }
 
   // If a comparator is present, use it.
   if (comparator) {
     var comparatorResult = comparator(leftHandOperand, rightHandOperand);
     // Comparators may return null, in which case we want to go back to default behavior.
     if (comparatorResult === false || comparatorResult === true) {
       memoizeSet(leftHandOperand, rightHandOperand, options.memoize, comparatorResult);
       return comparatorResult;
     }
     // To allow comparators to override *any* behavior, we ran them first. Since it didn't decide
     // what to do, we need to make sure to return the basic tests first before we move on.
     var simpleResult = simpleEqual(leftHandOperand, rightHandOperand);
     if (simpleResult !== null) {
       // Don't memoize this, it takes longer to set/retrieve than to just compare.
       return simpleResult;
     }
   }
 
   var leftHandType = type(leftHandOperand);
   if (leftHandType !== type(rightHandOperand)) {
     memoizeSet(leftHandOperand, rightHandOperand, options.memoize, false);
     return false;
   }
 
   // Temporarily set the operands in the memoize object to prevent blowing the stack
   memoizeSet(leftHandOperand, rightHandOperand, options.memoize, true);
 
   var result = extensiveDeepEqualByType(leftHandOperand, rightHandOperand, leftHandType, options);
   memoizeSet(leftHandOperand, rightHandOperand, options.memoize, result);
   return result;
 }
 
 function extensiveDeepEqualByType(leftHandOperand, rightHandOperand, leftHandType, options) {
   switch (leftHandType) {
     case 'String':
     case 'Number':
     case 'Boolean':
     case 'Date':
       // If these types are their instance types (e.g. `new Number`) then re-deepEqual against their values
       return deepEqual(leftHandOperand.valueOf(), rightHandOperand.valueOf());
     case 'Promise':
     case 'Symbol':
     case 'function':
     case 'WeakMap':
     case 'WeakSet':
     case 'Error':
       return leftHandOperand === rightHandOperand;
     case 'Arguments':
     case 'Int8Array':
     case 'Uint8Array':
     case 'Uint8ClampedArray':
     case 'Int16Array':
     case 'Uint16Array':
     case 'Int32Array':
     case 'Uint32Array':
     case 'Float32Array':
     case 'Float64Array':
     case 'Array':
       return iterableEqual(leftHandOperand, rightHandOperand, options);
     case 'RegExp':
       return regexpEqual(leftHandOperand, rightHandOperand);
     case 'Generator':
       return generatorEqual(leftHandOperand, rightHandOperand, options);
     case 'DataView':
       return iterableEqual(new Uint8Array(leftHandOperand.buffer), new Uint8Array(rightHandOperand.buffer), options);
     case 'ArrayBuffer':
       return iterableEqual(new Uint8Array(leftHandOperand), new Uint8Array(rightHandOperand), options);
     case 'Set':
       return entriesEqual(leftHandOperand, rightHandOperand, options);
     case 'Map':
       return entriesEqual(leftHandOperand, rightHandOperand, options);
     default:
       return objectEqual(leftHandOperand, rightHandOperand, options);
   }
 }
 
 /*!
  * Compare two Regular Expressions for equality.
  *
  * @param {RegExp} leftHandOperand
  * @param {RegExp} rightHandOperand
  * @return {Boolean} result
  */
 
 function regexpEqual(leftHandOperand, rightHandOperand) {
   return leftHandOperand.toString() === rightHandOperand.toString();
 }
 
 /*!
  * Compare two Sets/Maps for equality. Faster than other equality functions.
  *
  * @param {Set} leftHandOperand
  * @param {Set} rightHandOperand
  * @param {Object} [options] (Optional)
  * @return {Boolean} result
  */
 
 function entriesEqual(leftHandOperand, rightHandOperand, options) {
   // IE11 doesn't support Set#entries or Set#@@iterator, so we need manually populate using Set#forEach
   if (leftHandOperand.size !== rightHandOperand.size) {
     return false;
   }
   if (leftHandOperand.size === 0) {
     return true;
   }
   var leftHandItems = [];
   var rightHandItems = [];
   leftHandOperand.forEach(function gatherEntries(key, value) {
     leftHandItems.push([ key, value ]);
   });
   rightHandOperand.forEach(function gatherEntries(key, value) {
     rightHandItems.push([ key, value ]);
   });
   return iterableEqual(leftHandItems.sort(), rightHandItems.sort(), options);
 }
 
 /*!
  * Simple equality for flat iterable objects such as Arrays, TypedArrays or Node.js buffers.
  *
  * @param {Iterable} leftHandOperand
  * @param {Iterable} rightHandOperand
  * @param {Object} [options] (Optional)
  * @return {Boolean} result
  */
 
 function iterableEqual(leftHandOperand, rightHandOperand, options) {
   var length = leftHandOperand.length;
   if (length !== rightHandOperand.length) {
     return false;
   }
   if (length === 0) {
     return true;
   }
   var index = -1;
   while (++index < length) {
     if (deepEqual(leftHandOperand[index], rightHandOperand[index], options) === false) {
       return false;
     }
   }
   return true;
 }
 
 /*!
  * Simple equality for generator objects such as those returned by generator functions.
  *
  * @param {Iterable} leftHandOperand
  * @param {Iterable} rightHandOperand
  * @param {Object} [options] (Optional)
  * @return {Boolean} result
  */
 
 function generatorEqual(leftHandOperand, rightHandOperand, options) {
   return iterableEqual(getGeneratorEntries(leftHandOperand), getGeneratorEntries(rightHandOperand), options);
 }
 
 /*!
  * Determine if the given object has an @@iterator function.
  *
  * @param {Object} target
  * @return {Boolean} `true` if the object has an @@iterator function.
  */
 function hasIteratorFunction(target) {
   return typeof Symbol !== 'undefined' &&
     typeof target === 'object' &&
     typeof Symbol.iterator !== 'undefined' &&
     typeof target[Symbol.iterator] === 'function';
 }
 
 /*!
  * Gets all iterator entries from the given Object. If the Object has no @@iterator function, returns an empty array.
  * This will consume the iterator - which could have side effects depending on the @@iterator implementation.
  *
  * @param {Object} target
  * @returns {Array} an array of entries from the @@iterator function
  */
 function getIteratorEntries(target) {
   if (hasIteratorFunction(target)) {
     try {
       return getGeneratorEntries(target[Symbol.iterator]());
     } catch (iteratorError) {
       return [];
     }
   }
   return [];
 }
 
 /*!
  * Gets all entries from a Generator. This will consume the generator - which could have side effects.
  *
  * @param {Generator} target
  * @returns {Array} an array of entries from the Generator.
  */
 function getGeneratorEntries(generator) {
   var generatorResult = generator.next();
   var accumulator = [ generatorResult.value ];
   while (generatorResult.done === false) {
     generatorResult = generator.next();
     accumulator.push(generatorResult.value);
   }
   return accumulator;
 }
 
 /*!
  * Gets all own and inherited enumerable keys from a target.
  *
  * @param {Object} target
  * @returns {Array} an array of own and inherited enumerable keys from the target.
  */
 function getEnumerableKeys(target) {
   var keys = [];
   for (var key in target) {
     keys.push(key);
   }
   return keys;
 }
 
 /*!
  * Determines if two objects have matching values, given a set of keys. Defers to deepEqual for the equality check of
  * each key. If any value of the given key is not equal, the function will return false (early).
  *
  * @param {Mixed} leftHandOperand
  * @param {Mixed} rightHandOperand
  * @param {Array} keys An array of keys to compare the values of leftHandOperand and rightHandOperand against
  * @param {Object} [options] (Optional)
  * @return {Boolean} result
  */
 function keysEqual(leftHandOperand, rightHandOperand, keys, options) {
   var length = keys.length;
   if (length === 0) {
     return true;
   }
   for (var i = 0; i < length; i += 1) {
     if (deepEqual(leftHandOperand[keys[i]], rightHandOperand[keys[i]], options) === false) {
       return false;
     }
   }
   return true;
 }
 
 /*!
  * Recursively check the equality of two Objects. Once basic sameness has been established it will defer to `deepEqual`
  * for each enumerable key in the object.
  *
  * @param {Mixed} leftHandOperand
  * @param {Mixed} rightHandOperand
  * @param {Object} [options] (Optional)
  * @return {Boolean} result
  */
 
 function objectEqual(leftHandOperand, rightHandOperand, options) {
   var leftHandKeys = getEnumerableKeys(leftHandOperand);
   var rightHandKeys = getEnumerableKeys(rightHandOperand);
   if (leftHandKeys.length && leftHandKeys.length === rightHandKeys.length) {
     leftHandKeys.sort();
     rightHandKeys.sort();
     if (iterableEqual(leftHandKeys, rightHandKeys) === false) {
       return false;
     }
     return keysEqual(leftHandOperand, rightHandOperand, leftHandKeys, options);
   }
 
   var leftHandEntries = getIteratorEntries(leftHandOperand);
   var rightHandEntries = getIteratorEntries(rightHandOperand);
   if (leftHandEntries.length && leftHandEntries.length === rightHandEntries.length) {
     leftHandEntries.sort();
     rightHandEntries.sort();
     return iterableEqual(leftHandEntries, rightHandEntries, options);
   }
 
   if (leftHandKeys.length === 0 &&
       leftHandEntries.length === 0 &&
       rightHandKeys.length === 0 &&
       rightHandEntries.length === 0) {
     return true;
   }
 
   return false;
 }
 
 /*!
  * Returns true if the argument is a primitive.
  *
  * This intentionally returns true for all objects that can be compared by reference,
  * including functions and symbols.
  *
  * @param {Mixed} value
  * @return {Boolean} result
  */
 function isPrimitive(value) {
   return value === null || typeof value !== 'object';
 }
 
 },{"type-detect":39}],37:[function(require,module,exports){
 'use strict';
 
 /* !
  * Chai - getFuncName utility
  * Copyright(c) 2012-2016 Jake Luer <jake@alogicalparadox.com>
  * MIT Licensed
  */
 
 /**
  * ### .getFuncName(constructorFn)
  *
  * Returns the name of a function.
  * When a non-function instance is passed, returns `null`.
  * This also includes a polyfill function if `aFunc.name` is not defined.
  *
  * @name getFuncName
  * @param {Function} funct
  * @namespace Utils
  * @api public
  */
 
 var toString = Function.prototype.toString;
 var functionNameMatch = /\s*function(?:\s|\s*\/\*[^(?:*\/)]+\*\/\s*)*([^\s\(\/]+)/;
 function getFuncName(aFunc) {
   if (typeof aFunc !== 'function') {
     return null;
   }
 
   var name = '';
   if (typeof Function.prototype.name === 'undefined' && typeof aFunc.name === 'undefined') {
     // Here we run a polyfill if Function does not support the `name` property and if aFunc.name is not defined
     var match = toString.call(aFunc).match(functionNameMatch);
     if (match) {
       name = match[1];
     }
   } else {
     // If we've got a `name` property we just use it
     name = aFunc.name;
   }
 
   return name;
 }
 
 module.exports = getFuncName;
 
 },{}],38:[function(require,module,exports){
 'use strict';
 
 /* !
  * Chai - pathval utility
  * Copyright(c) 2012-2014 Jake Luer <jake@alogicalparadox.com>
  * @see https://github.com/logicalparadox/filtr
  * MIT Licensed
  */
 
 /**
  * ### .hasProperty(object, name)
  *
  * This allows checking whether an object has own
  * or inherited from prototype chain named property.
  *
  * Basically does the same thing as the `in`
  * operator but works properly with null/undefined values
  * and other primitives.
  *
  *     var obj = {
  *         arr: ['a', 'b', 'c']
  *       , str: 'Hello'
  *     }
  *
  * The following would be the results.
  *
  *     hasProperty(obj, 'str');  // true
  *     hasProperty(obj, 'constructor');  // true
  *     hasProperty(obj, 'bar');  // false
  *
  *     hasProperty(obj.str, 'length'); // true
  *     hasProperty(obj.str, 1);  // true
  *     hasProperty(obj.str, 5);  // false
  *
  *     hasProperty(obj.arr, 'length');  // true
  *     hasProperty(obj.arr, 2);  // true
  *     hasProperty(obj.arr, 3);  // false
  *
  * @param {Object} object
  * @param {String|Symbol} name
  * @returns {Boolean} whether it exists
  * @namespace Utils
  * @name hasProperty
  * @api public
  */
 
 function hasProperty(obj, name) {
   if (typeof obj === 'undefined' || obj === null) {
     return false;
   }
 
   // The `in` operator does not work with primitives.
   return name in Object(obj);
 }
 
 /* !
  * ## parsePath(path)
  *
  * Helper function used to parse string object
  * paths. Use in conjunction with `internalGetPathValue`.
  *
  *      var parsed = parsePath('myobject.property.subprop');
  *
  * ### Paths:
  *
  * * Can be infinitely deep and nested.
  * * Arrays are also valid using the formal `myobject.document[3].property`.
  * * Literal dots and brackets (not delimiter) must be backslash-escaped.
  *
  * @param {String} path
  * @returns {Object} parsed
  * @api private
  */
 
 function parsePath(path) {
   var str = path.replace(/([^\\])\[/g, '$1.[');
   var parts = str.match(/(\\\.|[^.]+?)+/g);
   return parts.map(function mapMatches(value) {
     if (
       value === 'constructor' ||
       value === '__proto__' ||
       value === 'prototype'
     ) {
       return {};
     }
     var regexp = /^\[(\d+)\]$/;
     var mArr = regexp.exec(value);
     var parsed = null;
     if (mArr) {
       parsed = { i: parseFloat(mArr[1]) };
     } else {
       parsed = { p: value.replace(/\\([.[\]])/g, '$1') };
     }
 
     return parsed;
   });
 }
 
 /* !
  * ## internalGetPathValue(obj, parsed[, pathDepth])
  *
  * Helper companion function for `.parsePath` that returns
  * the value located at the parsed address.
  *
  *      var value = getPathValue(obj, parsed);
  *
  * @param {Object} object to search against
  * @param {Object} parsed definition from `parsePath`.
  * @param {Number} depth (nesting level) of the property we want to retrieve
  * @returns {Object|Undefined} value
  * @api private
  */
 
 function internalGetPathValue(obj, parsed, pathDepth) {
   var temporaryValue = obj;
   var res = null;
   pathDepth = typeof pathDepth === 'undefined' ? parsed.length : pathDepth;
 
   for (var i = 0; i < pathDepth; i++) {
     var part = parsed[i];
     if (temporaryValue) {
       if (typeof part.p === 'undefined') {
         temporaryValue = temporaryValue[part.i];
       } else {
         temporaryValue = temporaryValue[part.p];
       }
 
       if (i === pathDepth - 1) {
         res = temporaryValue;
       }
     }
   }
 
   return res;
 }
 
 /* !
  * ## internalSetPathValue(obj, value, parsed)
  *
  * Companion function for `parsePath` that sets
  * the value located at a parsed address.
  *
  *  internalSetPathValue(obj, 'value', parsed);
  *
  * @param {Object} object to search and define on
  * @param {*} value to use upon set
  * @param {Object} parsed definition from `parsePath`
  * @api private
  */
 
 function internalSetPathValue(obj, val, parsed) {
   var tempObj = obj;
   var pathDepth = parsed.length;
   var part = null;
   // Here we iterate through every part of the path
   for (var i = 0; i < pathDepth; i++) {
     var propName = null;
     var propVal = null;
     part = parsed[i];
 
     // If it's the last part of the path, we set the 'propName' value with the property name
     if (i === pathDepth - 1) {
       propName = typeof part.p === 'undefined' ? part.i : part.p;
       // Now we set the property with the name held by 'propName' on object with the desired val
       tempObj[propName] = val;
     } else if (typeof part.p !== 'undefined' && tempObj[part.p]) {
       tempObj = tempObj[part.p];
     } else if (typeof part.i !== 'undefined' && tempObj[part.i]) {
       tempObj = tempObj[part.i];
     } else {
       // If the obj doesn't have the property we create one with that name to define it
       var next = parsed[i + 1];
       // Here we set the name of the property which will be defined
       propName = typeof part.p === 'undefined' ? part.i : part.p;
       // Here we decide if this property will be an array or a new object
       propVal = typeof next.p === 'undefined' ? [] : {};
       tempObj[propName] = propVal;
       tempObj = tempObj[propName];
     }
   }
 }
 
 /**
  * ### .getPathInfo(object, path)
  *
  * This allows the retrieval of property info in an
  * object given a string path.
  *
  * The path info consists of an object with the
  * following properties:
  *
  * * parent - The parent object of the property referenced by `path`
  * * name - The name of the final property, a number if it was an array indexer
  * * value - The value of the property, if it exists, otherwise `undefined`
  * * exists - Whether the property exists or not
  *
  * @param {Object} object
  * @param {String} path
  * @returns {Object} info
  * @namespace Utils
  * @name getPathInfo
  * @api public
  */
 
 function getPathInfo(obj, path) {
   var parsed = parsePath(path);
   var last = parsed[parsed.length - 1];
   var info = {
     parent:
       parsed.length > 1 ?
         internalGetPathValue(obj, parsed, parsed.length - 1) :
         obj,
     name: last.p || last.i,
     value: internalGetPathValue(obj, parsed),
   };
   info.exists = hasProperty(info.parent, info.name);
 
   return info;
 }
 
 /**
  * ### .getPathValue(object, path)
  *
  * This allows the retrieval of values in an
  * object given a string path.
  *
  *     var obj = {
  *         prop1: {
  *             arr: ['a', 'b', 'c']
  *           , str: 'Hello'
  *         }
  *       , prop2: {
  *             arr: [ { nested: 'Universe' } ]
  *           , str: 'Hello again!'
  *         }
  *     }
  *
  * The following would be the results.
  *
  *     getPathValue(obj, 'prop1.str'); // Hello
  *     getPathValue(obj, 'prop1.att[2]'); // b
  *     getPathValue(obj, 'prop2.arr[0].nested'); // Universe
  *
  * @param {Object} object
  * @param {String} path
  * @returns {Object} value or `undefined`
  * @namespace Utils
  * @name getPathValue
  * @api public
  */
 
 function getPathValue(obj, path) {
   var info = getPathInfo(obj, path);
   return info.value;
 }
 
 /**
  * ### .setPathValue(object, path, value)
  *
  * Define the value in an object at a given string path.
  *
  * ```js
  * var obj = {
  *     prop1: {
  *         arr: ['a', 'b', 'c']
  *       , str: 'Hello'
  *     }
  *   , prop2: {
  *         arr: [ { nested: 'Universe' } ]
  *       , str: 'Hello again!'
  *     }
  * };
  * ```
  *
  * The following would be acceptable.
  *
  * ```js
  * var properties = require('tea-properties');
  * properties.set(obj, 'prop1.str', 'Hello Universe!');
  * properties.set(obj, 'prop1.arr[2]', 'B');
  * properties.set(obj, 'prop2.arr[0].nested.value', { hello: 'universe' });
  * ```
  *
  * @param {Object} object
  * @param {String} path
  * @param {Mixed} value
  * @api private
  */
 
 function setPathValue(obj, path, val) {
   var parsed = parsePath(path);
   internalSetPathValue(obj, val, parsed);
   return obj;
 }
 
 module.exports = {
   hasProperty: hasProperty,
   getPathInfo: getPathInfo,
   getPathValue: getPathValue,
   setPathValue: setPathValue,
 };
 
 },{}],39:[function(require,module,exports){
 (function (global, factory) {
 	typeof exports === 'object' && typeof module !== 'undefined' ? module.exports = factory() :
 	typeof define === 'function' && define.amd ? define(factory) :
 	(global.typeDetect = factory());
 }(this, (function () { 'use strict';
 
 /* !
  * type-detect
  * Copyright(c) 2013 jake luer <jake@alogicalparadox.com>
  * MIT Licensed
  */
 var promiseExists = typeof Promise === 'function';
 
 /* eslint-disable no-undef */
 var globalObject = typeof self === 'object' ? self : global; // eslint-disable-line id-blacklist
 
 var symbolExists = typeof Symbol !== 'undefined';
 var mapExists = typeof Map !== 'undefined';
 var setExists = typeof Set !== 'undefined';
 var weakMapExists = typeof WeakMap !== 'undefined';
 var weakSetExists = typeof WeakSet !== 'undefined';
 var dataViewExists = typeof DataView !== 'undefined';
 var symbolIteratorExists = symbolExists && typeof Symbol.iterator !== 'undefined';
 var symbolToStringTagExists = symbolExists && typeof Symbol.toStringTag !== 'undefined';
 var setEntriesExists = setExists && typeof Set.prototype.entries === 'function';
 var mapEntriesExists = mapExists && typeof Map.prototype.entries === 'function';
 var setIteratorPrototype = setEntriesExists && Object.getPrototypeOf(new Set().entries());
 var mapIteratorPrototype = mapEntriesExists && Object.getPrototypeOf(new Map().entries());
 var arrayIteratorExists = symbolIteratorExists && typeof Array.prototype[Symbol.iterator] === 'function';
 var arrayIteratorPrototype = arrayIteratorExists && Object.getPrototypeOf([][Symbol.iterator]());
 var stringIteratorExists = symbolIteratorExists && typeof String.prototype[Symbol.iterator] === 'function';
 var stringIteratorPrototype = stringIteratorExists && Object.getPrototypeOf(''[Symbol.iterator]());
 var toStringLeftSliceLength = 8;
 var toStringRightSliceLength = -1;
 /**
  * ### typeOf (obj)
  *
  * Uses `Object.prototype.toString` to determine the type of an object,
  * normalising behaviour across engine versions & well optimised.
  *
  * @param {Mixed} object
  * @return {String} object type
  * @api public
  */
 function typeDetect(obj) {
   /* ! Speed optimisation
    * Pre:
    *   string literal     x 3,039,035 ops/sec ±1.62% (78 runs sampled)
    *   boolean literal    x 1,424,138 ops/sec ±4.54% (75 runs sampled)
    *   number literal     x 1,653,153 ops/sec ±1.91% (82 runs sampled)
    *   undefined          x 9,978,660 ops/sec ±1.92% (75 runs sampled)
    *   function           x 2,556,769 ops/sec ±1.73% (77 runs sampled)
    * Post:
    *   string literal     x 38,564,796 ops/sec ±1.15% (79 runs sampled)
    *   boolean literal    x 31,148,940 ops/sec ±1.10% (79 runs sampled)
    *   number literal     x 32,679,330 ops/sec ±1.90% (78 runs sampled)
    *   undefined          x 32,363,368 ops/sec ±1.07% (82 runs sampled)
    *   function           x 31,296,870 ops/sec ±0.96% (83 runs sampled)
    */
   var typeofObj = typeof obj;
   if (typeofObj !== 'object') {
     return typeofObj;
   }
 
   /* ! Speed optimisation
    * Pre:
    *   null               x 28,645,765 ops/sec ±1.17% (82 runs sampled)
    * Post:
    *   null               x 36,428,962 ops/sec ±1.37% (84 runs sampled)
    */
   if (obj === null) {
     return 'null';
   }
 
   /* ! Spec Conformance
    * Test: `Object.prototype.toString.call(window)``
    *  - Node === "[object global]"
    *  - Chrome === "[object global]"
    *  - Firefox === "[object Window]"
    *  - PhantomJS === "[object Window]"
    *  - Safari === "[object Window]"
    *  - IE 11 === "[object Window]"
    *  - IE Edge === "[object Window]"
    * Test: `Object.prototype.toString.call(this)``
    *  - Chrome Worker === "[object global]"
    *  - Firefox Worker === "[object DedicatedWorkerGlobalScope]"
    *  - Safari Worker === "[object DedicatedWorkerGlobalScope]"
    *  - IE 11 Worker === "[object WorkerGlobalScope]"
    *  - IE Edge Worker === "[object WorkerGlobalScope]"
    */
   if (obj === globalObject) {
     return 'global';
   }
 
   /* ! Speed optimisation
    * Pre:
    *   array literal      x 2,888,352 ops/sec ±0.67% (82 runs sampled)
    * Post:
    *   array literal      x 22,479,650 ops/sec ±0.96% (81 runs sampled)
    */
   if (
     Array.isArray(obj) &&
     (symbolToStringTagExists === false || !(Symbol.toStringTag in obj))
   ) {
     return 'Array';
   }
 
   // Not caching existence of `window` and related properties due to potential
   // for `window` to be unset before tests in quasi-browser environments.
   if (typeof window === 'object' && window !== null) {
     /* ! Spec Conformance
      * (https://html.spec.whatwg.org/multipage/browsers.html#location)
      * WhatWG HTML$7.7.3 - The `Location` interface
      * Test: `Object.prototype.toString.call(window.location)``
      *  - IE <=11 === "[object Object]"
      *  - IE Edge <=13 === "[object Object]"
      */
     if (typeof window.location === 'object' && obj === window.location) {
       return 'Location';
     }
 
     /* ! Spec Conformance
      * (https://html.spec.whatwg.org/#document)
      * WhatWG HTML$3.1.1 - The `Document` object
      * Note: Most browsers currently adher to the W3C DOM Level 2 spec
      *       (https://www.w3.org/TR/DOM-Level-2-HTML/html.html#ID-26809268)
      *       which suggests that browsers should use HTMLTableCellElement for
      *       both TD and TH elements. WhatWG separates these.
      *       WhatWG HTML states:
      *         > For historical reasons, Window objects must also have a
      *         > writable, configurable, non-enumerable property named
      *         > HTMLDocument whose value is the Document interface object.
      * Test: `Object.prototype.toString.call(document)``
      *  - Chrome === "[object HTMLDocument]"
      *  - Firefox === "[object HTMLDocument]"
      *  - Safari === "[object HTMLDocument]"
      *  - IE <=10 === "[object Document]"
      *  - IE 11 === "[object HTMLDocument]"
      *  - IE Edge <=13 === "[object HTMLDocument]"
      */
     if (typeof window.document === 'object' && obj === window.document) {
       return 'Document';
     }
 
     if (typeof window.navigator === 'object') {
       /* ! Spec Conformance
        * (https://html.spec.whatwg.org/multipage/webappapis.html#mimetypearray)
        * WhatWG HTML$8.6.1.5 - Plugins - Interface MimeTypeArray
        * Test: `Object.prototype.toString.call(navigator.mimeTypes)``
        *  - IE <=10 === "[object MSMimeTypesCollection]"
        */
       if (typeof window.navigator.mimeTypes === 'object' &&
           obj === window.navigator.mimeTypes) {
         return 'MimeTypeArray';
       }
 
       /* ! Spec Conformance
        * (https://html.spec.whatwg.org/multipage/webappapis.html#pluginarray)
        * WhatWG HTML$8.6.1.5 - Plugins - Interface PluginArray
        * Test: `Object.prototype.toString.call(navigator.plugins)``
        *  - IE <=10 === "[object MSPluginsCollection]"
        */
       if (typeof window.navigator.plugins === 'object' &&
           obj === window.navigator.plugins) {
         return 'PluginArray';
       }
     }
 
     if ((typeof window.HTMLElement === 'function' ||
         typeof window.HTMLElement === 'object') &&
         obj instanceof window.HTMLElement) {
       /* ! Spec Conformance
       * (https://html.spec.whatwg.org/multipage/webappapis.html#pluginarray)
       * WhatWG HTML$4.4.4 - The `blockquote` element - Interface `HTMLQuoteElement`
       * Test: `Object.prototype.toString.call(document.createElement('blockquote'))``
       *  - IE <=10 === "[object HTMLBlockElement]"
       */
       if (obj.tagName === 'BLOCKQUOTE') {
         return 'HTMLQuoteElement';
       }
 
       /* ! Spec Conformance
        * (https://html.spec.whatwg.org/#htmltabledatacellelement)
        * WhatWG HTML$4.9.9 - The `td` element - Interface `HTMLTableDataCellElement`
        * Note: Most browsers currently adher to the W3C DOM Level 2 spec
        *       (https://www.w3.org/TR/DOM-Level-2-HTML/html.html#ID-82915075)
        *       which suggests that browsers should use HTMLTableCellElement for
        *       both TD and TH elements. WhatWG separates these.
        * Test: Object.prototype.toString.call(document.createElement('td'))
        *  - Chrome === "[object HTMLTableCellElement]"
        *  - Firefox === "[object HTMLTableCellElement]"
        *  - Safari === "[object HTMLTableCellElement]"
        */
       if (obj.tagName === 'TD') {
         return 'HTMLTableDataCellElement';
       }
 
       /* ! Spec Conformance
        * (https://html.spec.whatwg.org/#htmltableheadercellelement)
        * WhatWG HTML$4.9.9 - The `td` element - Interface `HTMLTableHeaderCellElement`
        * Note: Most browsers currently adher to the W3C DOM Level 2 spec
        *       (https://www.w3.org/TR/DOM-Level-2-HTML/html.html#ID-82915075)
        *       which suggests that browsers should use HTMLTableCellElement for
        *       both TD and TH elements. WhatWG separates these.
        * Test: Object.prototype.toString.call(document.createElement('th'))
        *  - Chrome === "[object HTMLTableCellElement]"
        *  - Firefox === "[object HTMLTableCellElement]"
        *  - Safari === "[object HTMLTableCellElement]"
        */
       if (obj.tagName === 'TH') {
         return 'HTMLTableHeaderCellElement';
       }
     }
   }
 
   /* ! Speed optimisation
   * Pre:
   *   Float64Array       x 625,644 ops/sec ±1.58% (80 runs sampled)
   *   Float32Array       x 1,279,852 ops/sec ±2.91% (77 runs sampled)
   *   Uint32Array        x 1,178,185 ops/sec ±1.95% (83 runs sampled)
   *   Uint16Array        x 1,008,380 ops/sec ±2.25% (80 runs sampled)
   *   Uint8Array         x 1,128,040 ops/sec ±2.11% (81 runs sampled)
   *   Int32Array         x 1,170,119 ops/sec ±2.88% (80 runs sampled)
   *   Int16Array         x 1,176,348 ops/sec ±5.79% (86 runs sampled)
   *   Int8Array          x 1,058,707 ops/sec ±4.94% (77 runs sampled)
   *   Uint8ClampedArray  x 1,110,633 ops/sec ±4.20% (80 runs sampled)
   * Post:
   *   Float64Array       x 7,105,671 ops/sec ±13.47% (64 runs sampled)
   *   Float32Array       x 5,887,912 ops/sec ±1.46% (82 runs sampled)
   *   Uint32Array        x 6,491,661 ops/sec ±1.76% (79 runs sampled)
   *   Uint16Array        x 6,559,795 ops/sec ±1.67% (82 runs sampled)
   *   Uint8Array         x 6,463,966 ops/sec ±1.43% (85 runs sampled)
   *   Int32Array         x 5,641,841 ops/sec ±3.49% (81 runs sampled)
   *   Int16Array         x 6,583,511 ops/sec ±1.98% (80 runs sampled)
   *   Int8Array          x 6,606,078 ops/sec ±1.74% (81 runs sampled)
   *   Uint8ClampedArray  x 6,602,224 ops/sec ±1.77% (83 runs sampled)
   */
   var stringTag = (symbolToStringTagExists && obj[Symbol.toStringTag]);
   if (typeof stringTag === 'string') {
     return stringTag;
   }
 
   var objPrototype = Object.getPrototypeOf(obj);
   /* ! Speed optimisation
   * Pre:
   *   regex literal      x 1,772,385 ops/sec ±1.85% (77 runs sampled)
   *   regex constructor  x 2,143,634 ops/sec ±2.46% (78 runs sampled)
   * Post:
   *   regex literal      x 3,928,009 ops/sec ±0.65% (78 runs sampled)
   *   regex constructor  x 3,931,108 ops/sec ±0.58% (84 runs sampled)
   */
   if (objPrototype === RegExp.prototype) {
     return 'RegExp';
   }
 
   /* ! Speed optimisation
   * Pre:
   *   date               x 2,130,074 ops/sec ±4.42% (68 runs sampled)
   * Post:
   *   date               x 3,953,779 ops/sec ±1.35% (77 runs sampled)
   */
   if (objPrototype === Date.prototype) {
     return 'Date';
   }
 
   /* ! Spec Conformance
    * (http://www.ecma-international.org/ecma-262/6.0/index.html#sec-promise.prototype-@@tostringtag)
    * ES6$25.4.5.4 - Promise.prototype[@@toStringTag] should be "Promise":
    * Test: `Object.prototype.toString.call(Promise.resolve())``
    *  - Chrome <=47 === "[object Object]"
    *  - Edge <=20 === "[object Object]"
    *  - Firefox 29-Latest === "[object Promise]"
    *  - Safari 7.1-Latest === "[object Promise]"
    */
   if (promiseExists && objPrototype === Promise.prototype) {
     return 'Promise';
   }
 
   /* ! Speed optimisation
   * Pre:
   *   set                x 2,222,186 ops/sec ±1.31% (82 runs sampled)
   * Post:
   *   set                x 4,545,879 ops/sec ±1.13% (83 runs sampled)
   */
   if (setExists && objPrototype === Set.prototype) {
     return 'Set';
   }
 
   /* ! Speed optimisation
   * Pre:
   *   map                x 2,396,842 ops/sec ±1.59% (81 runs sampled)
   * Post:
   *   map                x 4,183,945 ops/sec ±6.59% (82 runs sampled)
   */
   if (mapExists && objPrototype === Map.prototype) {
     return 'Map';
   }
 
   /* ! Speed optimisation
   * Pre:
   *   weakset            x 1,323,220 ops/sec ±2.17% (76 runs sampled)
   * Post:
   *   weakset            x 4,237,510 ops/sec ±2.01% (77 runs sampled)
   */
   if (weakSetExists && objPrototype === WeakSet.prototype) {
     return 'WeakSet';
   }
 
   /* ! Speed optimisation
   * Pre:
   *   weakmap            x 1,500,260 ops/sec ±2.02% (78 runs sampled)
   * Post:
   *   weakmap            x 3,881,384 ops/sec ±1.45% (82 runs sampled)
   */
   if (weakMapExists && objPrototype === WeakMap.prototype) {
     return 'WeakMap';
   }
 
   /* ! Spec Conformance
    * (http://www.ecma-international.org/ecma-262/6.0/index.html#sec-dataview.prototype-@@tostringtag)
    * ES6$24.2.4.21 - DataView.prototype[@@toStringTag] should be "DataView":
    * Test: `Object.prototype.toString.call(new DataView(new ArrayBuffer(1)))``
    *  - Edge <=13 === "[object Object]"
    */
   if (dataViewExists && objPrototype === DataView.prototype) {
     return 'DataView';
   }
 
   /* ! Spec Conformance
    * (http://www.ecma-international.org/ecma-262/6.0/index.html#sec-%mapiteratorprototype%-@@tostringtag)
    * ES6$23.1.5.2.2 - %MapIteratorPrototype%[@@toStringTag] should be "Map Iterator":
    * Test: `Object.prototype.toString.call(new Map().entries())``
    *  - Edge <=13 === "[object Object]"
    */
   if (mapExists && objPrototype === mapIteratorPrototype) {
     return 'Map Iterator';
   }
 
   /* ! Spec Conformance
    * (http://www.ecma-international.org/ecma-262/6.0/index.html#sec-%setiteratorprototype%-@@tostringtag)
    * ES6$23.2.5.2.2 - %SetIteratorPrototype%[@@toStringTag] should be "Set Iterator":
    * Test: `Object.prototype.toString.call(new Set().entries())``
    *  - Edge <=13 === "[object Object]"
    */
   if (setExists && objPrototype === setIteratorPrototype) {
     return 'Set Iterator';
   }
 
   /* ! Spec Conformance
    * (http://www.ecma-international.org/ecma-262/6.0/index.html#sec-%arrayiteratorprototype%-@@tostringtag)
    * ES6$22.1.5.2.2 - %ArrayIteratorPrototype%[@@toStringTag] should be "Array Iterator":
    * Test: `Object.prototype.toString.call([][Symbol.iterator]())``
    *  - Edge <=13 === "[object Object]"
    */
   if (arrayIteratorExists && objPrototype === arrayIteratorPrototype) {
     return 'Array Iterator';
   }
 
   /* ! Spec Conformance
    * (http://www.ecma-international.org/ecma-262/6.0/index.html#sec-%stringiteratorprototype%-@@tostringtag)
    * ES6$21.1.5.2.2 - %StringIteratorPrototype%[@@toStringTag] should be "String Iterator":
    * Test: `Object.prototype.toString.call(''[Symbol.iterator]())``
    *  - Edge <=13 === "[object Object]"
    */
   if (stringIteratorExists && objPrototype === stringIteratorPrototype) {
     return 'String Iterator';
   }
 
   /* ! Speed optimisation
   * Pre:
   *   object from null   x 2,424,320 ops/sec ±1.67% (76 runs sampled)
   * Post:
   *   object from null   x 5,838,000 ops/sec ±0.99% (84 runs sampled)
   */
   if (objPrototype === null) {
     return 'Object';
   }
 
   return Object
     .prototype
     .toString
     .call(obj)
     .slice(toStringLeftSliceLength, toStringRightSliceLength);
 }
 
 return typeDetect;
 
 })));
 
 },{}]},{},[1])(1)
 });