File: test/js/ComparisonFailure.js

            /**
             * 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 Test
             * @extends AssertionError
             * @module test
             * @class ComparisonFailure
             * @constructor
             */
            YUITest.ComparisonFailure = function (message, expected, actual){
            
                //call superclass
                YUITest.AssertionError.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 from YUITest.AssertionError
            YUITest.ComparisonFailure.prototype = new YUITest.AssertionError;
            
            //restore constructor
            YUITest.ComparisonFailure.prototype.constructor = YUITest.ComparisonFailure;
            
            /**
             * Returns a fully formatted error for an assertion failure. This message
             * provides information about the expected and actual values.
             * @method getMessage
             * @return {String} A string describing the error.
             */
            YUITest.ComparisonFailure.prototype.getMessage = function(){
                return this.message + "\nExpected: " + this.expected + " (" + (typeof this.expected) + ")"  +
                        "\nActual: " + this.actual + " (" + (typeof this.actual) + ")";
            };