assert.js

/*!
 * 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 stricty 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` property with the expected value.
   *
   *     assert.lengthOf([1,2,3], 3, 'array has length of 3');
   *     assert.lengthOf('foobar', 6, 'string has length of 6');
   *
   * @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 doesNotHaveAllKeys
   * @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, [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 doesNotDecrease
   * @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');
};