# Yahoo! UI Library

### test 3.0.0b1

Yahoo! UI Library > test > Assert.js (source view)
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        /**
         * The Assert object provides functions to test JavaScript values against
         * known and expected results. Whenever a comparison (assertion) fails,
         * an error is thrown.
         *
         * @class Assert
         * @static
         */
        Y.Assert = {

            /**
             * The number of assertions performed.
             * @property _asserts
             * @type int
             * @private
             */
            _asserts: 0,

            //-------------------------------------------------------------------------
            // Helper Methods
            //-------------------------------------------------------------------------

            /**
             * Formats a message so that it can contain the original assertion message
             * in addition to the custom message.
             * @param {String} customMessage The message passed in by the developer.
             * @param {String} defaultMessage The message created by the error by default.
             * @return {String} The final error message, containing either or both.
             * @protected
             * @static
             * @method _formatMessage
             */
            _formatMessage : function (customMessage, defaultMessage) {
                var message = customMessage;
                if (Y.Lang.isString(customMessage) && customMessage.length > 0){
                    return Y.Lang.substitute(customMessage, { message: defaultMessage });
                } else {
                    return defaultMessage;
                }
            },

            /**
             * Returns the number of assertions that have been performed.
             * @method _getCount
             * @protected
             * @static
             */
            _getCount: function(){
                return this._asserts;
            },

            /**
             * Increments the number of assertions that have been performed.
             * @method _increment
             * @protected
             * @static
             */
            _increment: function(){
                this._asserts++;
            },

            /**
             * Resets the number of assertions that have been performed to 0.
             * @method _reset
             * @protected
             * @static
             */
            _reset: function(){
                this._asserts = 0;
            },

            //-------------------------------------------------------------------------
            // Generic Assertion Methods
            //-------------------------------------------------------------------------

            /**
             * Forces an assertion error to occur.
             * @param {String} message (Optional) The message to display with the failure.
             * @method fail
             * @static
             */
            fail : function (message) {
                throw new Y.Assert.Error(Y.Assert._formatMessage(message, "Test force-failed."));
            },

            //-------------------------------------------------------------------------
            // Equality Assertion Methods
            //-------------------------------------------------------------------------

            /**
             * Asserts that a value is equal to another. This uses the double equals sign
             * so type cohersion may occur.
             * @param {Object} expected The expected value.
             * @param {Object} actual The actual value to test.
             * @param {String} message (Optional) The message to display if the assertion fails.
             * @method areEqual
             * @static
             */
            areEqual : function (expected, actual, message) {
                Y.Assert._increment();
                if (expected != actual) {
                    throw new Y.Assert.ComparisonFailure(Y.Assert._formatMessage(message, "Values should be equal."), expected, actual);
                }
            },

            /**
             * Asserts that a value is not equal to another. This uses the double equals sign
             * so type cohersion may occur.
             * @param {Object} unexpected The unexpected value.
             * @param {Object} actual The actual value to test.
             * @param {String} message (Optional) The message to display if the assertion fails.
             * @method areNotEqual
             * @static
             */
            areNotEqual : function (unexpected, actual,
                                 message) {
                Y.Assert._increment();
                if (unexpected == actual) {
                    throw new Y.Assert.UnexpectedValue(Y.Assert._formatMessage(message, "Values should not be equal."), unexpected);
                }
            },

            /**
             * Asserts that a value is not the same as another. This uses the triple equals sign
             * so no type cohersion may occur.
             * @param {Object} unexpected The unexpected value.
             * @param {Object} actual The actual value to test.
             * @param {String} message (Optional) The message to display if the assertion fails.
             * @method areNotSame
             * @static
             */
            areNotSame : function (unexpected, actual, message) {
                Y.Assert._increment();
                if (unexpected === actual) {
                    throw new Y.Assert.UnexpectedValue(Y.Assert._formatMessage(message, "Values should not be the same."), unexpected);
                }
            },

            /**
             * Asserts that a value is the same as another. This uses the triple equals sign
             * so no type cohersion may occur.
             * @param {Object} expected The expected value.
             * @param {Object} actual The actual value to test.
             * @param {String} message (Optional) The message to display if the assertion fails.
             * @method areSame
             * @static
             */
            areSame : function (expected, actual, message) {
                Y.Assert._increment();
                if (expected !== actual) {
                    throw new Y.Assert.ComparisonFailure(Y.Assert._formatMessage(message, "Values should be the same."), expected, actual);
                }
            },

            //-------------------------------------------------------------------------
            // Boolean Assertion Methods
            //-------------------------------------------------------------------------

            /**
             * Asserts that a value is false. This uses the triple equals sign
             * so no type cohersion may occur.
             * @param {Object} actual The actual value to test.
             * @param {String} message (Optional) The message to display if the assertion fails.
             * @method isFalse
             * @static
             */
            isFalse : function (actual, message) {
                Y.Assert._increment();
                if (false !== actual) {
                    throw new Y.Assert.ComparisonFailure(Y.Assert._formatMessage(message, "Value should be false."), false, actual);
                }
            },

            /**
             * Asserts that a value is true. This uses the triple equals sign
             * so no type cohersion may occur.
             * @param {Object} actual The actual value to test.
             * @param {String} message (Optional) The message to display if the assertion fails.
             * @method isTrue
             * @static
             */
            isTrue : function (actual, message) {
                Y.Assert._increment();
                if (true !== actual) {
                    throw new Y.Assert.ComparisonFailure(Y.Assert._formatMessage(message, "Value should be true."), true, actual);
                }

            },

            //-------------------------------------------------------------------------
            // Special Value Assertion Methods
            //-------------------------------------------------------------------------

            /**
             * Asserts that a value is not a number.
             * @param {Object} actual The value to test.
             * @param {String} message (Optional) The message to display if the assertion fails.
             * @method isNaN
             * @static
             */
            isNaN : function (actual, message){
                Y.Assert._increment();
                if (!isNaN(actual)){
                    throw new Y.Assert.ComparisonFailure(Y.Assert._formatMessage(message, "Value should be NaN."), NaN, actual);
                }
            },

            /**
             * Asserts that a value is not the special NaN value.
             * @param {Object} actual The value to test.
             * @param {String} message (Optional) The message to display if the assertion fails.
             * @method isNotNaN
             * @static
             */
            isNotNaN : function (actual, message){
                Y.Assert._increment();
                if (isNaN(actual)){
                    throw new Y.Assert.UnexpectedValue(Y.Assert._formatMessage(message, "Values should not be NaN."), NaN);
                }
            },

            /**
             * Asserts that a value is not null. This uses the triple equals sign
             * so no type cohersion may occur.
             * @param {Object} actual The actual value to test.
             * @param {String} message (Optional) The message to display if the assertion fails.
             * @method isNotNull
             * @static
             */
            isNotNull : function (actual, message) {
                Y.Assert._increment();
                if (Y.Lang.isNull(actual)) {
                    throw new Y.Assert.UnexpectedValue(Y.Assert._formatMessage(message, "Values should not be null."), null);
                }
            },

            /**
             * Asserts that a value is not undefined. This uses the triple equals sign
             * so no type cohersion may occur.
             * @param {Object} actual The actual value to test.
             * @param {String} message (Optional) The message to display if the assertion fails.
             * @method isNotUndefined
             * @static
             */
            isNotUndefined : function (actual, message) {
                Y.Assert._increment();
                if (Y.Lang.isUndefined(actual)) {
                    throw new Y.Assert.UnexpectedValue(Y.Assert._formatMessage(message, "Value should not be undefined."), undefined);
                }
            },

            /**
             * Asserts that a value is null. This uses the triple equals sign
             * so no type cohersion may occur.
             * @param {Object} actual The actual value to test.
             * @param {String} message (Optional) The message to display if the assertion fails.
             * @method isNull
             * @static
             */
            isNull : function (actual, message) {
                Y.Assert._increment();
                if (!Y.Lang.isNull(actual)) {
                    throw new Y.Assert.ComparisonFailure(Y.Assert._formatMessage(message, "Value should be null."), null, actual);
                }
            },

            /**
             * Asserts that a value is undefined. This uses the triple equals sign
             * so no type cohersion may occur.
             * @param {Object} actual The actual value to test.
             * @param {String} message (Optional) The message to display if the assertion fails.
             * @method isUndefined
             * @static
             */
            isUndefined : function (actual, message) {
                Y.Assert._increment();
                if (!Y.Lang.isUndefined(actual)) {
                    throw new Y.Assert.ComparisonFailure(Y.Assert._formatMessage(message, "Value should be undefined."), undefined, actual);
                }
            },

            //--------------------------------------------------------------------------
            // Instance Assertion Methods
            //--------------------------------------------------------------------------

            /**
             * Asserts that a value is an array.
             * @param {Object} actual The value to test.
             * @param {String} message (Optional) The message to display if the assertion fails.
             * @method isArray
             * @static
             */
            isArray : function (actual, message) {
                Y.Assert._increment();
                if (!Y.Lang.isArray(actual)){
                    throw new Y.Assert.UnexpectedValue(Y.Assert._formatMessage(message, "Value should be an array."), actual);
                }
            },

            /**
             * Asserts that a value is a Boolean.
             * @param {Object} actual The value to test.
             * @param {String} message (Optional) The message to display if the assertion fails.
             * @method isBoolean
             * @static
             */
            isBoolean : function (actual, message) {
                Y.Assert._increment();
                if (!Y.Lang.isBoolean(actual)){
                    throw new Y.Assert.UnexpectedValue(Y.Assert._formatMessage(message, "Value should be a Boolean."), actual);
                }
            },

            /**
             * Asserts that a value is a function.
             * @param {Object} actual The value to test.
             * @param {String} message (Optional) The message to display if the assertion fails.
             * @method isFunction
             * @static
             */
            isFunction : function (actual, message) {
                Y.Assert._increment();
                if (!Y.Lang.isFunction(actual)){
                    throw new Y.Assert.UnexpectedValue(Y.Assert._formatMessage(message, "Value should be a function."), actual);
                }
            },

            /**
             * Asserts that a value is an instance of a particular object. This may return
             * incorrect results when comparing objects from one frame to constructors in
             * another frame. For best results, don't use in a cross-frame manner.
             * @param {Function} expected The function that the object should be an instance of.
             * @param {Object} actual The object to test.
             * @param {String} message (Optional) The message to display if the assertion fails.
             * @method isInstanceOf
             * @static
             */
            isInstanceOf : function (expected, actual, message) {
                Y.Assert._increment();
                if (!(actual instanceof expected)){
                    throw new Y.Assert.ComparisonFailure(Y.Assert._formatMessage(message, "Value isn't an instance of expected type."), expected, actual);
                }
            },

            /**
             * Asserts that a value is a number.
             * @param {Object} actual The value to test.
             * @param {String} message (Optional) The message to display if the assertion fails.
             * @method isNumber
             * @static
             */
            isNumber : function (actual, message) {
                Y.Assert._increment();
                if (!Y.Lang.isNumber(actual)){
                    throw new Y.Assert.UnexpectedValue(Y.Assert._formatMessage(message, "Value should be a number."), actual);
                }
            },

            /**
             * Asserts that a value is an object.
             * @param {Object} actual The value to test.
             * @param {String} message (Optional) The message to display if the assertion fails.
             * @method isObject
             * @static
             */
            isObject : function (actual, message) {
                Y.Assert._increment();
                if (!Y.Lang.isObject(actual)){
                    throw new Y.Assert.UnexpectedValue(Y.Assert._formatMessage(message, "Value should be an object."), actual);
                }
            },

            /**
             * Asserts that a value is a string.
             * @param {Object} actual The value to test.
             * @param {String} message (Optional) The message to display if the assertion fails.
             * @method isString
             * @static
             */
            isString : function (actual, message) {
                Y.Assert._increment();
                if (!Y.Lang.isString(actual)){
                    throw new Y.Assert.UnexpectedValue(Y.Assert._formatMessage(message, "Value should be a string."), actual);
                }
            },

            /**
             * Asserts that a value is of a particular type.
             * @param {String} expectedType The expected type of the variable.
             * @param {Object} actualValue The actual value to test.
             * @param {String} message (Optional) The message to display if the assertion fails.
             * @method isTypeOf
             * @static
             */
            isTypeOf : function (expectedType, actualValue, message){
                Y.Assert._increment();
                if (typeof actualValue != expectedType){
                    throw new Y.Assert.ComparisonFailure(Y.Assert._formatMessage(message, "Value should be of type " + expectedType + "."), expected, typeof actualValue);
                }
            }
        };

        /**
         * Asserts that a given condition is true. If not, then a Y.Assert.Error object is thrown
         * and the test fails.
         * @method Y.assert
         * @param {Boolean} condition The condition to test.
         * @param {String} message The message to display if the assertion fails.
         * @static
         */
        Y.assert = function(condition, message){
            Y.Assert._increment();
            if (!condition){
                throw new Y.Assert.Error(Y.Assert._formatMessage(message, "Assertion failed."));
            }
        };

        /**
         * Forces an assertion error to occur. Shortcut for Y.Assert.fail().
         * @method Y.fail
         * @param {String} message (Optional) The message to display with the failure.
         * @static
         */
        Y.fail = Y.Assert.fail;

        //-----------------------------------------------------------------------------
        // Assertion errors
        //-----------------------------------------------------------------------------

        /**
         * Error is thrown whenever an assertion fails. It provides methods
         * to more easily get at error information and also provides a base class
         * from which more specific assertion errors can be derived.
         *
         * @param {String} message The message to display when the error occurs.
         * @namespace Assert
         * @class Error
         * @constructor
         */
        Y.Assert.Error = function (message){

            //call superclass
            arguments.callee.superclass.constructor.call(this, message);

            /*
             * Error message. Must be duplicated to ensure browser receives it.
             * @type String
             * @property message
             */
            this.message = message;

            /**
             * The name of the error that occurred.
             * @type String
             * @property name
             */
            this.name = "Assert Error";
        };

        //inherit methods
        Y.extend(Y.Assert.Error, Error, {

            /**
             * Returns a fully formatted error for an assertion failure. This should
             * be overridden by all subclasses to provide specific information.
             * @method getMessage
             * @return {String} A string describing the error.
             */
            getMessage : function () {
                return this.message;
            },

            /**
             * Returns a string representation of the error.
             * @method toString
             * @return {String} A string representation of the error.
             */
            toString : function () {
                return this.name + ": " + this.getMessage();
            },

            /**
             * Returns a primitive value version of the error. Same as toString().
             * @method valueOf
             * @return {String} A primitive value version of the error.
             */
            valueOf : function () {
                return this.toString();
            }

        });

        /**
         * ComparisonFailure is subclass of Error that is thrown whenever
         * a comparison between two values fails. It provides mechanisms to retrieve
         * both the expected and actual value.
         *
         * @param {String} message The message to display when the error occurs.
         * @param {Object} expected The expected value.
         * @param {Object} actual The actual value that caused the assertion to fail.
         * @namespace Assert
         * @extends Assert.Error
         * @class ComparisonFailure
         * @constructor
         */
        Y.Assert.ComparisonFailure = function (message, expected, actual){

            //call superclass
            arguments.callee.superclass.constructor.call(this, message);

            /**
             * The expected value.
             * @type Object
             * @property expected
             */
            this.expected = expected;

            /**
             * The actual value.
             * @type Object
             * @property actual
             */
            this.actual = actual;

            /**
             * The name of the error that occurred.
             * @type String
             * @property name
             */
            this.name = "ComparisonFailure";

        };

        //inherit methods
        Y.extend(Y.Assert.ComparisonFailure, Y.Assert.Error, {

            /**
             * Returns a fully formatted error for an assertion failure. This message
             * provides information about the expected and actual values.
             * @method toString
             * @return {String} A string describing the error.
             */
            getMessage : function () {
                return this.message + "\nExpected: " + this.expected + " (" + (typeof this.expected) + ")"  +
                    "\nActual:" + this.actual + " (" + (typeof this.actual) + ")";
            }

        });

        /**
         * UnexpectedValue is subclass of Error that is thrown whenever
         * a value was unexpected in its scope. This typically means that a test
         * was performed to determine that a value was *not* equal to a certain
         * value.
         *
         * @param {String} message The message to display when the error occurs.
         * @param {Object} unexpected The unexpected value.
         * @namespace Assert
         * @extends Assert.Error
         * @class UnexpectedValue
         * @constructor
         */
        Y.Assert.UnexpectedValue = function (message, unexpected){

            //call superclass
            arguments.callee.superclass.constructor.call(this, message);

            /**
             * The unexpected value.
             * @type Object
             * @property unexpected
             */
            this.unexpected = unexpected;

            /**
             * The name of the error that occurred.
             * @type String
             * @property name
             */
            this.name = "UnexpectedValue";

        };

        //inherit methods
        Y.extend(Y.Assert.UnexpectedValue, Y.Assert.Error, {

            /**
             * Returns a fully formatted error for an assertion failure. The message
             * contains information about the unexpected value that was encountered.
             * @method getMessage
             * @return {String} A string describing the error.
             */
            getMessage : function () {
                return this.message + "\nUnexpected: " + this.unexpected + " (" + (typeof this.unexpected) + ") ";
            }

        });

        /**
         * ShouldFail is subclass of Error that is thrown whenever
         * a test was expected to fail but did not.
         *
         * @param {String} message The message to display when the error occurs.
         * @namespace Assert
         * @extends Assert.Error
         * @class ShouldFail
         * @constructor
         */
        Y.Assert.ShouldFail = function (message){

            //call superclass
            arguments.callee.superclass.constructor.call(this, message || "This test should fail but didn't.");

            /**
             * The name of the error that occurred.
             * @type String
             * @property name
             */
            this.name = "ShouldFail";

        };

        //inherit methods
        Y.extend(Y.Assert.ShouldFail, Y.Assert.Error);

        /**
         * ShouldError is subclass of Error that is thrown whenever
         * a test is expected to throw an error but doesn't.
         *
         * @param {String} message The message to display when the error occurs.
         * @namespace Assert
         * @extends Assert.Error
         * @class ShouldError
         * @constructor
         */
        Y.Assert.ShouldError = function (message){

            //call superclass
            arguments.callee.superclass.constructor.call(this, message || "This test should have thrown an error but didn't.");

            /**
             * The name of the error that occurred.
             * @type String
             * @property name
             */
            this.name = "ShouldError";

        };

        //inherit methods
        Y.extend(Y.Assert.ShouldError, Y.Assert.Error);

        /**
         * UnexpectedError is subclass of Error that is thrown whenever
         * an error occurs within the course of a test and the test was not expected
         * to throw an error.
         *
         * @param {Error} cause The unexpected error that caused this error to be
         *                      thrown.
         * @namespace Assert
         * @extends Assert.Error
         * @class UnexpectedError
         * @constructor
         */
        Y.Assert.UnexpectedError = function (cause){

            //call superclass
            arguments.callee.superclass.constructor.call(this, "Unexpected error: " + cause.message);

            /**
             * The unexpected error that occurred.
             * @type Error
             * @property cause
             */
            this.cause = cause;

            /**
             * The name of the error that occurred.
             * @type String
             * @property name
             */
            this.name = "UnexpectedError";

            /**
             * Stack information for the error (if provided).
             * @type String
             * @property stack
             */
            this.stack = cause.stack;

        };

        //inherit methods
        Y.extend(Y.Assert.UnexpectedError, Y.Assert.Error);

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