/* eslint-disable */

var exports = module.exports;

/**
 * Exports.
 */

module.exports = expect;
expect.Assertion = Assertion;

/**
 * Exports version.
 */

expect.version = '0.3.1';

/**
 * Possible assertion flags.
 */

var flags = {
    not: ['to', 'be', 'have', 'include', 'only']
  , to: ['be', 'have', 'include', 'only', 'not']
  , only: ['have']
  , have: ['own']
  , be: ['an']
};

function expect (obj) {
  return new Assertion(obj);
}

/**
 * Constructor
 *
 * @api private
 */

function Assertion (obj, flag, parent) {
  this.obj = obj;
  this.flags = {};

  if (undefined != parent) {
    this.flags[flag] = true;

    for (var i in parent.flags) {
      if (parent.flags.hasOwnProperty(i)) {
        this.flags[i] = true;
      }
    }
  }

  var $flags = flag ? flags[flag] : keys(flags)
    , self = this;

  if ($flags) {
    for (var i = 0, l = $flags.length; i < l; i++) {
      // avoid recursion
      if (this.flags[$flags[i]]) continue;

      var name = $flags[i]
        , assertion = new Assertion(this.obj, name, this)

      if ('function' == typeof Assertion.prototype[name]) {
        // clone the function, make sure we dont touch the prot reference
        var old = this[name];
        this[name] = function () {
          return old.apply(self, arguments);
        };

        for (var fn in Assertion.prototype) {
          if (Assertion.prototype.hasOwnProperty(fn) && fn != name) {
            if (typeof this[name] === 'function' && fn === 'length') {
              continue;
            }

            this[name][fn] = bind(assertion[fn], assertion);
          }
        }
      } else {
        this[name] = assertion;
      }
    }
  }
}

/**
 * Performs an assertion
 *
 * @api private
 */

Assertion.prototype.assert = function (truth, msg, error, expected) {
  var msg = this.flags.not ? error : msg
    , ok = this.flags.not ? !truth : truth
    , err;

  if (!ok) {
    err = new Error(msg.call(this));
    if (this.customMsg) {
      err.message = this.customMsg;
    }
    if (arguments.length > 3) {
      err.actual = this.obj;
      err.expected = expected;
      err.showDiff = true;
    }
    throw err;
  }

  this.and = new Assertion(this.obj);
};

/**
 * Check if the value is truthy
 *
 * @api public
 */

Assertion.prototype.ok = function () {
  this.assert(
      !!this.obj
    , function(){ return 'expected ' + i(this.obj) + ' to be truthy' }
    , function(){ return 'expected ' + i(this.obj) + ' to be falsy' });
};

/**
 * Creates an anonymous function which calls fn with arguments.
 *
 * @api public
 */

Assertion.prototype.withArgs = function() {
  expect(this.obj).to.be.a('function');
  var fn = this.obj;
  var args = Array.prototype.slice.call(arguments);
  return expect(function() { fn.apply(null, args); });
};

/**
 * Assert that the function throws.
 *
 * @param {Function|RegExp} callback, or regexp to match error string against
 * @api public
 */

Assertion.prototype['throw'] =
Assertion.prototype.throwError =
Assertion.prototype.throwException = function (fn) {
  expect(this.obj).to.be.a('function');

  var thrown = false
    , not = this.flags.not;

  try {
    this.obj();
  } catch (e) {
    if (isRegExp(fn)) {
      var subject = 'string' == typeof e ? e : e.message;
      if (not) {
        expect(subject).to.not.match(fn);
      } else {
        expect(subject).to.match(fn);
      }
    } else if ('function' == typeof fn) {
      fn(e);
    }
    thrown = true;
  }

  if (isRegExp(fn) && not) {
    // in the presence of a matcher, ensure the `not` only applies to
    // the matching.
    this.flags.not = false;
  }

  var name = this.obj.name || 'fn';
  this.assert(
      thrown
    , function(){ return 'expected ' + name + ' to throw an exception' }
    , function(){ return 'expected ' + name + ' not to throw an exception' });
};

/**
 * Checks if the array is empty.
 *
 * @api public
 */

Assertion.prototype.empty = function () {
  var expectation;

  if ('object' == typeof this.obj && null !== this.obj && !isArray(this.obj)) {
    if ('number' == typeof this.obj.length) {
      expectation = !this.obj.length;
    } else {
      expectation = !keys(this.obj).length;
    }
  } else {
    if ('string' != typeof this.obj) {
      expect(this.obj).to.be.an('object');
    }

    expect(this.obj).to.have.property('length');
    expectation = !this.obj.length;
  }

  this.assert(
      expectation
    , function(){ return 'expected ' + i(this.obj) + ' to be empty' }
    , function(){ return 'expected ' + i(this.obj) + ' to not be empty' });
  return this;
};

/**
 * Checks if the obj exactly equals another.
 *
 * @api public
 */

Assertion.prototype.be =
Assertion.prototype.equal = function (obj, msg) {
  if (typeof(msg) === 'string') {
    this.customMsg = msg;
  }
  this.assert(
      obj === this.obj
    , function(){ return 'expected ' + i(this.obj) + ' to equal ' + i(obj) }
    , function(){ return 'expected ' + i(this.obj) + ' to not equal ' + i(obj) });
  return this;
};

/**
 * Checks if the obj sortof equals another.
 *
 * @api public
 */

Assertion.prototype.eql = function (obj, msg) {
  if (typeof(msg) === 'string') {
    this.customMsg = msg;
  }
  this.assert(
      expect.eql(this.obj, obj)
    , function(){ return 'expected ' + i(this.obj) + ' to sort of equal ' + i(obj) }
    , function(){ return 'expected ' + i(this.obj) + ' to sort of not equal ' + i(obj) }
    , obj);
  return this;
};

/**
 * Assert within start to finish (inclusive).
 *
 * @param {Number} start
 * @param {Number} finish
 * @api public
 */

Assertion.prototype.within = function (start, finish, msg) {
  if (typeof(msg) === 'string') {
    this.customMsg = msg;
  }
  var range = start + '..' + finish;
  this.assert(
      this.obj >= start && this.obj <= finish
    , function(){ return 'expected ' + i(this.obj) + ' to be within ' + range }
    , function(){ return 'expected ' + i(this.obj) + ' to not be within ' + range });
  return this;
};

/**
 * Assert typeof / instance of
 *
 * @api public
 */

Assertion.prototype.a =
Assertion.prototype.an = function (type) {
  if ('string' == typeof type) {
    // proper english in error msg
    var n = /^[aeiou]/.test(type) ? 'n' : '';

    // typeof with support for 'array'
    this.assert(
        'array' == type ? isArray(this.obj) :
          'regexp' == type ? isRegExp(this.obj) :
            'object' == type
              ? 'object' == typeof this.obj && null !== this.obj
              : type == typeof this.obj
      , function(){ return 'expected ' + i(this.obj) + ' to be a' + n + ' ' + type }
      , function(){ return 'expected ' + i(this.obj) + ' not to be a' + n + ' ' + type });
  } else {
    // instanceof
    var name = type.name || 'supplied constructor';
    this.assert(
        this.obj instanceof type
      , function(){ return 'expected ' + i(this.obj) + ' to be an instance of ' + name }
      , function(){ return 'expected ' + i(this.obj) + ' not to be an instance of ' + name });
  }

  return this;
};

/**
 * Assert numeric value above _n_.
 *
 * @param {Number} n
 * @api public
 */

Assertion.prototype.greaterThan =
Assertion.prototype.above = function (n, msg) {
  if (typeof(msg) === 'string') {
    this.customMsg = msg;
  }
  this.assert(
      this.obj > n
    , function(){ return 'expected ' + i(this.obj) + ' to be above ' + n }
    , function(){ return 'expected ' + i(this.obj) + ' to be below ' + n });
  return this;
};

/**
 * Assert numeric value below _n_.
 *
 * @param {Number} n
 * @api public
 */

Assertion.prototype.lessThan =
Assertion.prototype.below = function (n, msg) {
  if (typeof(msg) === 'string') {
    this.customMsg = msg;
  }
  this.assert(
      this.obj < n
    , function(){ return 'expected ' + i(this.obj) + ' to be below ' + n }
    , function(){ return 'expected ' + i(this.obj) + ' to be above ' + n });
  return this;
};

/**
 * Assert string value matches _regexp_.
 *
 * @param {RegExp} regexp
 * @api public
 */

Assertion.prototype.match = function (regexp, msg) {
  if (typeof(msg) === 'string') {
    this.customMsg = msg;
  }
  this.assert(
      regexp.exec(this.obj)
    , function(){ return 'expected ' + i(this.obj) + ' to match ' + regexp }
    , function(){ return 'expected ' + i(this.obj) + ' not to match ' + regexp });
  return this;
};

/**
 * Assert property "length" exists and has value of _n_.
 *
 * @param {Number} n
 * @api public
 */

Assertion.prototype.length = function (n, msg) {
  if (typeof(msg) === 'string') {
    this.customMsg = msg;
  }
  expect(this.obj).to.have.property('length');
  var len = this.obj.length;
  this.assert(
      n == len
    , function(){ return 'expected ' + i(this.obj) + ' to have a length of ' + n + ' but got ' + len }
    , function(){ return 'expected ' + i(this.obj) + ' to not have a length of ' + len });
  return this;
};

/**
 * Assert property _name_ exists, with optional _val_.
 *
 * @param {String} name
 * @param {Mixed} val
 * @api public
 */

Assertion.prototype.property = function (name, val) {
  if (this.flags.own) {
    this.assert(
        Object.prototype.hasOwnProperty.call(this.obj, name)
      , function(){ return 'expected ' + i(this.obj) + ' to have own property ' + i(name) }
      , function(){ return 'expected ' + i(this.obj) + ' to not have own property ' + i(name) });
    return this;
  }

  if (this.flags.not && undefined !== val) {
    if (undefined === this.obj[name]) {
      throw new Error(i(this.obj) + ' has no property ' + i(name));
    }
  } else {
    var hasProp;
    try {
      hasProp = name in this.obj
    } catch (e) {
      hasProp = undefined !== this.obj[name]
    }

    this.assert(
        hasProp
      , function(){ return 'expected ' + i(this.obj) + ' to have a property ' + i(name) }
      , function(){ return 'expected ' + i(this.obj) + ' to not have a property ' + i(name) });
  }

  if (undefined !== val) {
    this.assert(
        val === this.obj[name]
      , function(){ return 'expected ' + i(this.obj) + ' to have a property ' + i(name)
        + ' of ' + i(val) + ', but got ' + i(this.obj[name]) }
      , function(){ return 'expected ' + i(this.obj) + ' to not have a property ' + i(name)
        + ' of ' + i(val) });
  }

  this.obj = this.obj[name];
  return this;
};

/**
 * Assert that the array contains _obj_ or string contains _obj_.
 *
 * @param {Mixed} obj|string
 * @api public
 */

Assertion.prototype.string =
Assertion.prototype.contain = function (obj, msg) {
  if (typeof(msg) === 'string') {
    this.customMsg = msg;
  }
  if ('string' == typeof this.obj) {
    this.assert(
        ~this.obj.indexOf(obj)
      , function(){ return 'expected ' + i(this.obj) + ' to contain ' + i(obj) }
      , function(){ return 'expected ' + i(this.obj) + ' to not contain ' + i(obj) });
  } else {
    this.assert(
        ~indexOf(this.obj, obj)
      , function(){ return 'expected ' + i(this.obj) + ' to contain ' + i(obj) }
      , function(){ return 'expected ' + i(this.obj) + ' to not contain ' + i(obj) });
  }
  return this;
};

/**
 * Assert exact keys or inclusion of keys by using
 * the `.own` modifier.
 *
 * @param {Array|String ...} keys
 * @api public
 */

Assertion.prototype.key =
Assertion.prototype.keys = function ($keys) {
  var str
    , ok = true;

  $keys = isArray($keys)
    ? $keys
    : Array.prototype.slice.call(arguments);

  if (!$keys.length) throw new Error('keys required');

  var actual = keys(this.obj)
    , len = $keys.length;

  // Inclusion
  ok = every($keys, function (key) {
    return ~indexOf(actual, key);
  });

  // Strict
  if (!this.flags.not && this.flags.only) {
    ok = ok && $keys.length == actual.length;
  }

  // Key string
  if (len > 1) {
    $keys = map($keys, function (key) {
      return i(key);
    });
    var last = $keys.pop();
    str = $keys.join(', ') + ', and ' + last;
  } else {
    str = i($keys[0]);
  }

  // Form
  str = (len > 1 ? 'keys ' : 'key ') + str;

  // Have / include
  str = (!this.flags.only ? 'include ' : 'only have ') + str;

  // Assertion
  this.assert(
      ok
    , function(){ return 'expected ' + i(this.obj) + ' to ' + str }
    , function(){ return 'expected ' + i(this.obj) + ' to not ' + str });

  return this;
};

/**
 * Assert a failure.
 *
 * @param {String ...} custom message
 * @api public
 */
Assertion.prototype.fail = function (msg) {
  var error = function() { return msg || "explicit failure"; }
  this.assert(false, error, error);
  return this;
};

/**
 * Function bind implementation.
 */

function bind (fn, scope) {
  return function () {
    return fn.apply(scope, arguments);
  }
}

/**
 * Array every compatibility
 *
 * @see bit.ly/5Fq1N2
 * @api public
 */

function every (arr, fn, thisObj) {
  var scope = thisObj || global;
  for (var i = 0, j = arr.length; i < j; ++i) {
    if (!fn.call(scope, arr[i], i, arr)) {
      return false;
    }
  }
  return true;
}

/**
 * Array indexOf compatibility.
 *
 * @see bit.ly/a5Dxa2
 * @api public
 */

function indexOf (arr, o, i) {
  if (Array.prototype.indexOf) {
    return Array.prototype.indexOf.call(arr, o, i);
  }

  if (arr.length === undefined) {
    return -1;
  }

  for (var j = arr.length, i = i < 0 ? i + j < 0 ? 0 : i + j : i || 0
      ; i < j && arr[i] !== o; i++);

  return j <= i ? -1 : i;
}

// https://gist.github.com/1044128/
var getOuterHTML = function(element) {
  if ('outerHTML' in element) return element.outerHTML;
  var ns = "http://www.w3.org/1999/xhtml";
  var container = document.createElementNS(ns, '_');
  var xmlSerializer = new XMLSerializer();
  var html;
  if (document.xmlVersion) {
    return xmlSerializer.serializeToString(element);
  } else {
    container.appendChild(element.cloneNode(false));
    html = container.innerHTML.replace('><', '>' + element.innerHTML + '<');
    container.innerHTML = '';
    return html;
  }
};

// Returns true if object is a DOM element.
var isDOMElement = function (object) {
  if (typeof HTMLElement === 'object') {
    return object instanceof HTMLElement;
  } else {
    return object &&
      typeof object === 'object' &&
      object.nodeType === 1 &&
      typeof object.nodeName === 'string';
  }
};

/**
 * Inspects an object.
 *
 * @see taken from node.js `util` module (copyright Joyent, MIT license)
 * @api private
 */

function i (obj, showHidden, depth) {
  var seen = [];

  function stylize (str) {
    return str;
  }

  function format (value, recurseTimes) {
    // Provide a hook for user-specified inspect functions.
    // Check that value is an object with an inspect function on it
    if (value && typeof value.inspect === 'function' &&
        // Filter out the util module, it's inspect function is special
        value !== exports &&
        // Also filter out any prototype objects using the circular check.
        !(value.constructor && value.constructor.prototype === value)) {
      return value.inspect(recurseTimes);
    }

    // Primitive types cannot have properties
    switch (typeof value) {
      case 'undefined':
        return stylize('undefined', 'undefined');

      case 'string':
        var simple = '\'' + JSON.stringify(value).replace(/^"|"$/g, '')
                                                  .replace(/'/g, "\\'")
                                                  .replace(/\\"/g, '"') + '\'';
        return stylize(simple, 'string');

      case 'number':
        return stylize('' + value, 'number');

      case 'boolean':
        return stylize('' + value, 'boolean');
    }
    // For some reason typeof null is "object", so special case here.
    if (value === null) {
      return stylize('null', 'null');
    }

    if (isDOMElement(value)) {
      return getOuterHTML(value);
    }

    // Look up the keys of the object.
    var visible_keys = keys(value);
    var $keys = showHidden ? Object.getOwnPropertyNames(value) : visible_keys;

    // Functions without properties can be shortcutted.
    if (typeof value === 'function' && $keys.length === 0) {
      if (isRegExp(value)) {
        return stylize('' + value, 'regexp');
      } else {
        var name = value.name ? ': ' + value.name : '';
        return stylize('[Function' + name + ']', 'special');
      }
    }

    // Dates without properties can be shortcutted
    if (isDate(value) && $keys.length === 0) {
      return stylize(value.toUTCString(), 'date');
    }

    // Error objects can be shortcutted
    if (value instanceof Error) {
      return stylize("["+value.toString()+"]", 'Error');
    }

    var base, type, braces;
    // Determine the object type
    if (isArray(value)) {
      type = 'Array';
      braces = ['[', ']'];
    } else {
      type = 'Object';
      braces = ['{', '}'];
    }

    // Make functions say that they are functions
    if (typeof value === 'function') {
      var n = value.name ? ': ' + value.name : '';
      base = (isRegExp(value)) ? ' ' + value : ' [Function' + n + ']';
    } else {
      base = '';
    }

    // Make dates with properties first say the date
    if (isDate(value)) {
      base = ' ' + value.toUTCString();
    }

    if ($keys.length === 0) {
      return braces[0] + base + braces[1];
    }

    if (recurseTimes < 0) {
      if (isRegExp(value)) {
        return stylize('' + value, 'regexp');
      } else {
        return stylize('[Object]', 'special');
      }
    }

    seen.push(value);

    var output = map($keys, function (key) {
      var name, str;
      if (value.__lookupGetter__) {
        if (value.__lookupGetter__(key)) {
          if (value.__lookupSetter__(key)) {
            str = stylize('[Getter/Setter]', 'special');
          } else {
            str = stylize('[Getter]', 'special');
          }
        } else {
          if (value.__lookupSetter__(key)) {
            str = stylize('[Setter]', 'special');
          }
        }
      }
      if (indexOf(visible_keys, key) < 0) {
        name = '[' + key + ']';
      }
      if (!str) {
        if (indexOf(seen, value[key]) < 0) {
          if (recurseTimes === null) {
            str = format(value[key]);
          } else {
            str = format(value[key], recurseTimes - 1);
          }
          if (str.indexOf('\n') > -1) {
            if (isArray(value)) {
              str = map(str.split('\n'), function (line) {
                return '  ' + line;
              }).join('\n').substr(2);
            } else {
              str = '\n' + map(str.split('\n'), function (line) {
                return '   ' + line;
              }).join('\n');
            }
          }
        } else {
          str = stylize('[Circular]', 'special');
        }
      }
      if (typeof name === 'undefined') {
        if (type === 'Array' && key.match(/^\d+$/)) {
          return str;
        }
        name = JSON.stringify('' + key);
        if (name.match(/^"([a-zA-Z_][a-zA-Z_0-9]*)"$/)) {
          name = name.substr(1, name.length - 2);
          name = stylize(name, 'name');
        } else {
          name = name.replace(/'/g, "\\'")
                      .replace(/\\"/g, '"')
                      .replace(/(^"|"$)/g, "'");
          name = stylize(name, 'string');
        }
      }

      return name + ': ' + str;
    });

    seen.pop();

    var numLinesEst = 0;
    var length = reduce(output, function (prev, cur) {
      numLinesEst++;
      if (indexOf(cur, '\n') >= 0) numLinesEst++;
      return prev + cur.length + 1;
    }, 0);

    if (length > 50) {
      output = braces[0] +
                (base === '' ? '' : base + '\n ') +
                ' ' +
                output.join(',\n  ') +
                ' ' +
                braces[1];

    } else {
      output = braces[0] + base + ' ' + output.join(', ') + ' ' + braces[1];
    }

    return output;
  }
  return format(obj, (typeof depth === 'undefined' ? 2 : depth));
}

expect.stringify = i;

function isArray (ar) {
  return Object.prototype.toString.call(ar) === '[object Array]';
}

function isRegExp(re) {
  var s;
  try {
    s = '' + re;
  } catch (e) {
    return false;
  }

  return re instanceof RegExp || // easy case
          // duck-type for context-switching evalcx case
          typeof(re) === 'function' &&
          re.constructor.name === 'RegExp' &&
          re.compile &&
          re.test &&
          re.exec &&
          s.match(/^\/.*\/[gim]{0,3}$/);
}

function isDate(d) {
  return d instanceof Date;
}

function keys (obj) {
  if (Object.keys) {
    return Object.keys(obj);
  }

  var keys = [];

  for (var i in obj) {
    if (Object.prototype.hasOwnProperty.call(obj, i)) {
      keys.push(i);
    }
  }

  return keys;
}

function map (arr, mapper, that) {
  if (Array.prototype.map) {
    return Array.prototype.map.call(arr, mapper, that);
  }

  var other= new Array(arr.length);

  for (var i= 0, n = arr.length; i<n; i++)
    if (i in arr)
      other[i] = mapper.call(that, arr[i], i, arr);

  return other;
}

function reduce (arr, fun) {
  if (Array.prototype.reduce) {
    return Array.prototype.reduce.apply(
        arr
      , Array.prototype.slice.call(arguments, 1)
    );
  }

  var len = +this.length;

  if (typeof fun !== "function")
    throw new TypeError();

  // no value to return if no initial value and an empty array
  if (len === 0 && arguments.length === 1)
    throw new TypeError();

  var i = 0;
  if (arguments.length >= 2) {
    var rv = arguments[1];
  } else {
    do {
      if (i in this) {
        rv = this[i++];
        break;
      }

      // if array contains no values, no initial value to return
      if (++i >= len)
        throw new TypeError();
    } while (true);
  }

  for (; i < len; i++) {
    if (i in this)
      rv = fun.call(null, rv, this[i], i, this);
  }

  return rv;
}

/**
 * Asserts deep equality
 *
 * @see taken from node.js `assert` module (copyright Joyent, MIT license)
 * @api private
 */

expect.eql = function eql(actual, expected) {
  // 7.1. All identical values are equivalent, as determined by ===.
  if (actual === expected) {
    return true;
  } else if ('undefined' != typeof Buffer
    && Buffer.isBuffer(actual) && Buffer.isBuffer(expected)) {
    if (actual.length != expected.length) return false;

    for (var i = 0; i < actual.length; i++) {
      if (actual[i] !== expected[i]) return false;
    }

    return true;

    // 7.2. If the expected value is a Date object, the actual value is
    // equivalent if it is also a Date object that refers to the same time.
  } else if (actual instanceof Date && expected instanceof Date) {
    return actual.getTime() === expected.getTime();

    // 7.3. Other pairs that do not both pass typeof value == "object",
    // equivalence is determined by ==.
  } else if (typeof actual != 'object' && typeof expected != 'object') {
    return actual == expected;
  // If both are regular expression use the special `regExpEquiv` method
  // to determine equivalence.
  } else if (isRegExp(actual) && isRegExp(expected)) {
    return regExpEquiv(actual, expected);
  // 7.4. For all other Object pairs, including Array objects, equivalence is
  // determined by having the same number of owned properties (as verified
  // with Object.prototype.hasOwnProperty.call), the same set of keys
  // (although not necessarily the same order), equivalent values for every
  // corresponding key, and an identical "prototype" property. Note: this
  // accounts for both named and indexed properties on Arrays.
  } else {
    return objEquiv(actual, expected);
  }
};

function isUndefinedOrNull (value) {
  return value === null || value === undefined;
}

function isArguments (object) {
  return Object.prototype.toString.call(object) == '[object Arguments]';
}

function regExpEquiv (a, b) {
  return a.source === b.source && a.global === b.global &&
          a.ignoreCase === b.ignoreCase && a.multiline === b.multiline;
}

function objEquiv (a, b) {
  if (isUndefinedOrNull(a) || isUndefinedOrNull(b))
    return false;
  // an identical "prototype" property.
  if (a.prototype !== b.prototype) return false;
  //~~~I've managed to break Object.keys through screwy arguments passing.
  //   Converting to array solves the problem.
  if (isArguments(a)) {
    if (!isArguments(b)) {
      return false;
    }
    a = pSlice.call(a);
    b = pSlice.call(b);
    return expect.eql(a, b);
  }
  try{
    var ka = keys(a),
      kb = keys(b),
      key, i;
  } catch (e) {//happens when one is a string literal and the other isn't
    return false;
  }
  // having the same number of owned properties (keys incorporates hasOwnProperty)
  if (ka.length != kb.length)
    return false;
  //the same set of keys (although not necessarily the same order),
  ka.sort();
  kb.sort();
  //~~~cheap key test
  for (i = ka.length - 1; i >= 0; i--) {
    if (ka[i] != kb[i])
      return false;
  }
  //equivalent values for every corresponding key, and
  //~~~possibly expensive deep test
  for (i = ka.length - 1; i >= 0; i--) {
    key = ka[i];
    if (!expect.eql(a[key], b[key]))
        return false;
  }
  return true;
}