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
   * @api public
   */

  var assert = chai.assert = function (express, errmsg) {
    var test = new Assertion(null, null, chai.assert);
    test.assert(
        express
      , errmsg
      , '[ negation message unavailable ]'
    );
  };

  /**
   * ### .fail(actual, expected, [message], [operator])
   *
   * Throw a failure. Node.js `assert` module-compatible.
   *
   * @name fail
   * @param {Mixed} actual
   * @param {Mixed} expected
   * @param {String} message
   * @param {String} operator
   * @api public
   */

  assert.fail = function (actual, expected, message, operator) {
    message = message || 'assert.fail()';
    throw new chai.AssertionError(message, {
        actual: actual
      , expected: expected
      , operator: operator
    }, assert.fail);
  };

  /**
   * ### .ok(object, [message])
   *
   * Asserts that `object` is truthy.
   *
   *     assert.ok('everything', 'everything is ok');
   *     assert.ok(false, 'this will fail');
   *
   * @name ok
   * @param {Mixed} object to test
   * @param {String} message
   * @api public
   */

  assert.ok = function (val, msg) {
    new Assertion(val, msg).is.ok;
  };

  /**
   * ### .notOk(object, [message])
   *
   * Asserts that `object` is falsy.
   *
   *     assert.notOk('everything', 'this will fail');
   *     assert.notOk(false, 'this will pass');
   *
   * @name notOk
   * @param {Mixed} object to test
   * @param {String} message
   * @api public
   */

  assert.notOk = function (val, msg) {
    new Assertion(val, msg).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
   * @api public
   */

  assert.equal = function (act, exp, msg) {
    var test = new Assertion(act, msg, assert.equal);

    test.assert(
        exp == flag(test, 'object')
      , 'expected #{this} to equal #{exp}'
      , 'expected #{this} to not equal #{act}'
      , exp
      , act
    );
  };

  /**
   * ### .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
   * @api public
   */

  assert.notEqual = function (act, exp, msg) {
    var test = new Assertion(act, msg, assert.notEqual);

    test.assert(
        exp != flag(test, 'object')
      , 'expected #{this} to not equal #{exp}'
      , 'expected #{this} to equal #{act}'
      , exp
      , act
    );
  };

  /**
   * ### .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
   * @api public
   */

  assert.strictEqual = function (act, exp, msg) {
    new Assertion(act, msg).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
   * @api public
   */

  assert.notStrictEqual = function (act, exp, msg) {
    new Assertion(act, msg).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
   * @api public
   */

  assert.deepEqual = function (act, exp, msg) {
    new Assertion(act, msg).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
   * @api public
   */

  assert.notDeepEqual = function (act, exp, msg) {
    new Assertion(act, msg).to.not.eql(exp);
  };

  /**
   * ### .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
   * @api public
   */

  assert.isAbove = function (val, abv, msg) {
    new Assertion(val, msg).to.be.above(abv);
  };

   /**
   * ### .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
   * @api public
   */

  assert.isBelow = function (val, blw, msg) {
    new Assertion(val, msg).to.be.below(blw);
  };

   /**
   * ### .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
   * @api public
   */

  assert.isTrue = function (val, msg) {
    new Assertion(val, msg).is['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
   * @api public
   */

  assert.isFalse = function (val, msg) {
    new Assertion(val, msg).is['false'];
  };

  /**
   * ### .isNull(value, [message])
   *
   * Asserts that `value` is null.
   *
   *     assert.isNull(err, 'there was no error');
   *
   * @name isNull
   * @param {Mixed} value
   * @param {String} message
   * @api public
   */

  assert.isNull = function (val, msg) {
    new Assertion(val, msg).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
   * @api public
   */

  assert.isNotNull = function (val, msg) {
    new Assertion(val, msg).to.not.equal(null);
  };

  /**
   * ### .isUndefined(value, [message])
   *
   * Asserts that `value` is `undefined`.
   *
   *     var tea;
   *     assert.isUndefined(tea, 'no tea defined');
   *
   * @name isUndefined
   * @param {Mixed} value
   * @param {String} message
   * @api public
   */

  assert.isUndefined = function (val, msg) {
    new Assertion(val, msg).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
   * @api public
   */

  assert.isDefined = function (val, msg) {
    new Assertion(val, msg).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
   * @api public
   */

  assert.isFunction = function (val, msg) {
    new Assertion(val, msg).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
   * @api public
   */

  assert.isNotFunction = function (val, msg) {
    new Assertion(val, msg).to.not.be.a('function');
  };

  /**
   * ### .isObject(value, [message])
   *
   * Asserts that `value` is an object (as revealed by
   * `Object.prototype.toString`).
   *
   *     var selection = { name: 'Chai', serve: 'with spices' };
   *     assert.isObject(selection, 'tea selection is an object');
   *
   * @name isObject
   * @param {Mixed} value
   * @param {String} message
   * @api public
   */

  assert.isObject = function (val, msg) {
    new Assertion(val, msg).to.be.a('object');
  };

  /**
   * ### .isNotObject(value, [message])
   *
   * Asserts that `value` is _not_ an object.
   *
   *     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
   * @api public
   */

  assert.isNotObject = function (val, msg) {
    new Assertion(val, msg).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
   * @api public
   */

  assert.isArray = function (val, msg) {
    new Assertion(val, msg).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
   * @api public
   */

  assert.isNotArray = function (val, msg) {
    new Assertion(val, msg).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
   * @api public
   */

  assert.isString = function (val, msg) {
    new Assertion(val, msg).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
   * @api public
   */

  assert.isNotString = function (val, msg) {
    new Assertion(val, msg).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
   * @api public
   */

  assert.isNumber = function (val, msg) {
    new Assertion(val, msg).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
   * @api public
   */

  assert.isNotNumber = function (val, msg) {
    new Assertion(val, msg).to.not.be.a('number');
  };

  /**
   * ### .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
   * @api public
   */

  assert.isBoolean = function (val, msg) {
    new Assertion(val, msg).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
   * @api public
   */

  assert.isNotBoolean = function (val, msg) {
    new Assertion(val, msg).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
   * @api public
   */

  assert.typeOf = function (val, type, msg) {
    new Assertion(val, msg).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
   * @api public
   */

  assert.notTypeOf = function (val, type, msg) {
    new Assertion(val, msg).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
   * @api public
   */

  assert.instanceOf = function (val, type, msg) {
    new Assertion(val, msg).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
   * @api public
   */

  assert.notInstanceOf = function (val, type, msg) {
    new Assertion(val, msg).to.not.be.instanceOf(type);
  };

  /**
   * ### .include(haystack, needle, [message])
   *
   * Asserts that `haystack` includes `needle`. Works
   * for strings and arrays.
   *
   *     assert.include('foobar', 'bar', 'foobar contains string "bar"');
   *     assert.include([ 1, 2, 3 ], 3, 'array contains value');
   *
   * @name include
   * @param {Array|String} haystack
   * @param {Mixed} needle
   * @param {String} message
   * @api public
   */

  assert.include = function (exp, inc, msg) {
    new Assertion(exp, msg, assert.include).include(inc);
  };

  /**
   * ### .notInclude(haystack, needle, [message])
   *
   * Asserts that `haystack` does not include `needle`. Works
   * for strings and arrays.
   *i
   *     assert.notInclude('foobar', 'baz', 'string not include substring');
   *     assert.notInclude([ 1, 2, 3 ], 4, 'array not include contain value');
   *
   * @name notInclude
   * @param {Array|String} haystack
   * @param {Mixed} needle
   * @param {String} message
   * @api public
   */

  assert.notInclude = function (exp, inc, msg) {
    new Assertion(exp, msg, assert.notInclude).not.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
   * @api public
   */

  assert.match = function (exp, re, msg) {
    new Assertion(exp, msg).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
   * @api public
   */

  assert.notMatch = function (exp, re, msg) {
    new Assertion(exp, msg).to.not.match(re);
  };

  /**
   * ### .property(object, property, [message])
   *
   * Asserts that `object` has a property named by `property`.
   *
   *     assert.property({ tea: { green: 'matcha' }}, 'tea');
   *
   * @name property
   * @param {Object} object
   * @param {String} property
   * @param {String} message
   * @api public
   */

  assert.property = function (obj, prop, msg) {
    new Assertion(obj, msg).to.have.property(prop);
  };

  /**
   * ### .notProperty(object, property, [message])
   *
   * Asserts that `object` does _not_ have a property named by `property`.
   *
   *     assert.notProperty({ tea: { green: 'matcha' }}, 'coffee');
   *
   * @name notProperty
   * @param {Object} object
   * @param {String} property
   * @param {String} message
   * @api public
   */

  assert.notProperty = function (obj, prop, msg) {
    new Assertion(obj, msg).to.not.have.property(prop);
  };

  /**
   * ### .deepProperty(object, property, [message])
   *
   * Asserts that `object` has a property named by `property`, which can be a
   * string using dot- and bracket-notation for deep reference.
   *
   *     assert.deepProperty({ tea: { green: 'matcha' }}, 'tea.green');
   *
   * @name deepProperty
   * @param {Object} object
   * @param {String} property
   * @param {String} message
   * @api public
   */

  assert.deepProperty = function (obj, prop, msg) {
    new Assertion(obj, msg).to.have.deep.property(prop);
  };

  /**
   * ### .notDeepProperty(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 deep reference.
   *
   *     assert.notDeepProperty({ tea: { green: 'matcha' }}, 'tea.oolong');
   *
   * @name notDeepProperty
   * @param {Object} object
   * @param {String} property
   * @param {String} message
   * @api public
   */

  assert.notDeepProperty = function (obj, prop, msg) {
    new Assertion(obj, msg).to.not.have.deep.property(prop);
  };

  /**
   * ### .propertyVal(object, property, value, [message])
   *
   * Asserts that `object` has a property named by `property` with value given
   * by `value`.
   *
   *     assert.propertyVal({ tea: 'is good' }, 'tea', 'is good');
   *
   * @name propertyVal
   * @param {Object} object
   * @param {String} property
   * @param {Mixed} value
   * @param {String} message
   * @api public
   */

  assert.propertyVal = function (obj, prop, val, msg) {
    new Assertion(obj, msg).to.have.property(prop, val);
  };

  /**
   * ### .propertyNotVal(object, property, value, [message])
   *
   * Asserts that `object` has a property named by `property`, but with a value
   * different from that given by `value`.
   *
   *     assert.propertyNotVal({ tea: 'is good' }, 'tea', 'is bad');
   *
   * @name propertyNotVal
   * @param {Object} object
   * @param {String} property
   * @param {Mixed} value
   * @param {String} message
   * @api public
   */

  assert.propertyNotVal = function (obj, prop, val, msg) {
    new Assertion(obj, msg).to.not.have.property(prop, val);
  };

  /**
   * ### .deepPropertyVal(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 deep
   * reference.
   *
   *     assert.deepPropertyVal({ tea: { green: 'matcha' }}, 'tea.green', 'matcha');
   *
   * @name deepPropertyVal
   * @param {Object} object
   * @param {String} property
   * @param {Mixed} value
   * @param {String} message
   * @api public
   */

  assert.deepPropertyVal = function (obj, prop, val, msg) {
    new Assertion(obj, msg).to.have.deep.property(prop, val);
  };

  /**
   * ### .deepPropertyNotVal(object, property, value, [message])
   *
   * Asserts that `object` has a property named by `property`, but with a value
   * different from that given by `value`. `property` can use dot- and
   * bracket-notation for deep reference.
   *
   *     assert.deepPropertyNotVal({ tea: { green: 'matcha' }}, 'tea.green', 'konacha');
   *
   * @name deepPropertyNotVal
   * @param {Object} object
   * @param {String} property
   * @param {Mixed} value
   * @param {String} message
   * @api public
   */

  assert.deepPropertyNotVal = function (obj, prop, val, msg) {
    new Assertion(obj, msg).to.not.have.deep.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', 5, 'string has length of 6');
   *
   * @name lengthOf
   * @param {Mixed} object
   * @param {Number} length
   * @param {String} message
   * @api public
   */

  assert.lengthOf = function (exp, len, msg) {
    new Assertion(exp, msg).to.have.length(len);
  };

  /**
   * ### .throws(function, [constructor/string/regexp], [string/regexp], [message])
   *
   * Asserts that `function` will throw an error that is an instance of
   * `constructor`, or alternately that it will throw an error with message
   * matching `regexp`.
   *
   *     assert.throw(fn, 'function throws a reference error');
   *     assert.throw(fn, /function throws a reference error/);
   *     assert.throw(fn, ReferenceError);
   *     assert.throw(fn, ReferenceError, 'function throws a reference error');
   *     assert.throw(fn, ReferenceError, /function throws a reference error/);
   *
   * @name throws
   * @alias throw
   * @alias Throw
   * @param {Function} function
   * @param {ErrorConstructor} constructor
   * @param {RegExp} regexp
   * @param {String} message
   * @see https://developer.mozilla.org/en/JavaScript/Reference/Global_Objects/Error#Error_types
   * @api public
   */

  assert.Throw = function (fn, errt, errs, msg) {
    if ('string' === typeof errt || errt instanceof RegExp) {
      errs = errt;
      errt = null;
    }

    var assertErr = new Assertion(fn, msg).to.Throw(errt, errs);
    return flag(assertErr, 'object');
  };

  /**
   * ### .doesNotThrow(function, [constructor/regexp], [message])
   *
   * Asserts that `function` will _not_ throw an error that is an instance of
   * `constructor`, or alternately that it will not throw an error with message
   * matching `regexp`.
   *
   *     assert.doesNotThrow(fn, Error, 'function does not throw');
   *
   * @name doesNotThrow
   * @param {Function} function
   * @param {ErrorConstructor} constructor
   * @param {RegExp} regexp
   * @param {String} message
   * @see https://developer.mozilla.org/en/JavaScript/Reference/Global_Objects/Error#Error_types
   * @api public
   */

  assert.doesNotThrow = function (fn, type, msg) {
    if ('string' === typeof type) {
      msg = type;
      type = null;
    }

    new Assertion(fn, msg).to.not.Throw(type);
  };

  /**
   * ### .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
   * @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:
        throw new Error('Invalid operator "' + operator + '"');
    }
    var test = new Assertion(ok, msg);
    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
   * @api public
   */

  assert.closeTo = function (act, exp, delta, msg) {
    new Assertion(act, msg).to.be.closeTo(exp, delta);
  };

  /**
   * ### .sameMembers(set1, set2, [message])
   *
   * Asserts that `set1` and `set2` have the same members.
   * Order is not taken into account.
   *
   *     assert.sameMembers([ 1, 2, 3 ], [ 2, 1, 3 ], 'same members');
   *
   * @name sameMembers
   * @param {Array} set1
   * @param {Array} set2
   * @param {String} message
   * @api public
   */

  assert.sameMembers = function (set1, set2, msg) {
    new Assertion(set1, msg).to.have.same.members(set2);
  }

  /**
   * ### .sameDeepMembers(set1, set2, [message])
   *
   * Asserts that `set1` and `set2` have the same members - using a deep equality checking.
   * Order is not taken into account.
   *
   *     assert.sameDeepMembers([ {b: 3}, {a: 2}, {c: 5} ], [ {c: 5}, {b: 3}, {a: 2} ], 'same deep members');
   *
   * @name sameDeepMembers
   * @param {Array} set1
   * @param {Array} set2
   * @param {String} message
   * @api public
   */

  assert.sameDeepMembers = function (set1, set2, msg) {
    new Assertion(set1, msg).to.have.same.deep.members(set2);
  }

  /**
   * ### .includeMembers(superset, subset, [message])
   *
   * Asserts that `subset` is included in `superset`.
   * Order is not taken into account.
   *
   *     assert.includeMembers([ 1, 2, 3 ], [ 2, 1 ], 'include members');
   *
   * @name includeMembers
   * @param {Array} superset
   * @param {Array} subset
   * @param {String} message
   * @api public
   */

  assert.includeMembers = function (superset, subset, msg) {
    new Assertion(superset, msg).to.include.members(subset);
  }

   /**
   * ### .changes(function, object, property)
   *
   * 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
   * @param {String} property name
   * @param {String} message _optional_
   * @api public
   */

  assert.changes = function (fn, obj, prop) {
    new Assertion(fn).to.change(obj, prop);
  }

   /**
   * ### .doesNotChange(function, object, property)
   *
   * Asserts that a function does not changes 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
   * @param {String} property name
   * @param {String} message _optional_
   * @api public
   */

  assert.doesNotChange = function (fn, obj, prop) {
    new Assertion(fn).to.not.change(obj, prop);
  }

   /**
   * ### .increases(function, object, property)
   *
   * Asserts that a function increases an 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
   * @param {String} property name
   * @param {String} message _optional_
   * @api public
   */

  assert.increases = function (fn, obj, prop) {
    new Assertion(fn).to.increase(obj, prop);
  }

   /**
   * ### .doesNotIncrease(function, object, property)
   *
   * Asserts that a function does not increase 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
   * @param {String} property name
   * @param {String} message _optional_
   * @api public
   */

  assert.doesNotIncrease = function (fn, obj, prop) {
    new Assertion(fn).to.not.increase(obj, prop);
  }

   /**
   * ### .decreases(function, object, property)
   *
   * Asserts that a function decreases an 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
   * @param {String} property name
   * @param {String} message _optional_
   * @api public
   */

  assert.decreases = function (fn, obj, prop) {
    new Assertion(fn).to.decrease(obj, prop);
  }

   /**
   * ### .doesNotDecrease(function, object, property)
   *
   * Asserts that a function does not decreases an 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
   * @param {String} property name
   * @param {String} message _optional_
   * @api public
   */

  assert.doesNotDecrease = function (fn, obj, prop) {
    new Assertion(fn).to.not.decrease(obj, prop);
  }

  /*!
   * Undocumented / untested
   */

  assert.ifError = function (val, msg) {
    new Assertion(val, msg).to.not.be.ok;
  };

  /*!
   * Aliases.
   */

  (function alias(name, as){
    assert[as] = assert[name];
    return alias;
  })
  ('Throw', 'throw')
  ('Throw', 'throws');
};