/**
                             * UnexpectedError is subclass of AssertionError 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 Test
                             * @extends YUITest.AssertionError
                             * @module test
                             * @class UnexpectedError
                             * @constructor
                             */
                            YUITest.UnexpectedError = function (cause){
                            
                                //call superclass
                                YUITest.AssertionError.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 from YUITest.AssertionError
                            YUITest.UnexpectedError.prototype = new YUITest.AssertionError();
                            
                            //restore constructor
                            YUITest.UnexpectedError.prototype.constructor = YUITest.UnexpectedError;