每次测试后重置服务对象

我想在我的AngularJS应用程序中测试我的Auth服务。

这是服务:

'use strict';
angular.module('testApp')
    .factory('Auth', function ($window, $http, $location, $q) {
        var currentUser;
        return {
            authenticate: function (email, password) {
                //promise to return
                var deferred = $q.defer();
                var authRequest = $http.post('https://' + $location.host() + ':3005/authenticate', {email: email, password: password});
                authRequest.success(function (data, status, header, config) {
                    //Store currentUser in sessionStorage
                    currentUser = data;
                    $window.sessionStorage.setItem('currentUser', JSON.stringify(currentUser));
                    //resolve promise
                    deferred.resolve();
                });
                authRequest.error(function (data, status, header, config) {
                    //reject promise
                    deferred.reject('Invalid credentials.');
                });
                return deferred.promise;
            },
            isAuthenticated: function () {
                return this.getCurrentUser() !== null;
            },
            getCurrentUser: function () {
                if (currentUser !== undefined) {
                    return currentUser;
                } else {
                    currentUser = JSON.parse($window.sessionStorage.getItem('currentUser'));
                    return currentUser;
                }
            },
            logOut: function () {
                var that = this;
                $http.get('https://' + $location.host() + ':3005/logout')
                    .success(function (data, status, header, config) {
                        that.appLogOut();
                        $location.path('/login');
                    }).
                    error(function (data, status, headers, config) {
                        console.log('logout error');
                    });
            },
            appLogOut: function () {
                console.log('appside log out');
                currentUser = null;
                $window.sessionStorage.removeItem('currentUser');
            }
        };
    });

这是我的测试:

'use strict';
describe('Service: Auth', function () {
    // load the service's module
    beforeEach(module('testApp'));
    // instantiate service and any mock objects
    var Auth,
        httpBackend;
    //http://code.angularjs.org/1.2.14/docs/api/ngMock/function/angular.mock.inject
    beforeEach(inject(function (_Auth_, $httpBackend) {
        Auth = _Auth_;
        httpBackend = $httpBackend;
    }));
    // verify that no expectations were missed in the tests
    afterEach(function () {
        httpBackend.verifyNoOutstandingExpectation();
        httpBackend.verifyNoOutstandingRequest();
    });
    it('should be instantiated', function () {
        (!!Auth).should.be.true;
    });
    describe('authenticate(email, password)', function () {
        var user = {
            email: 'shaun@test.com',
            password: 'password',
            sessionId: 'abc123'
        };
        it('should make a call to the server to log the user in - and FULFILL promise if response == 200', function () {
            httpBackend.whenPOST(/https:'/'/.+'/authenticate/, {
                email: user.email,
                password: user.password
            }).respond(200, user);
            var promise = Auth.authenticate(user.email, user.password);
            httpBackend.flush();
            promise.should.eventually.be.fulfilled;
        });    
    });

    describe('isAuthenticated()', function () {
        it('should return false if user is not authenticated', function () {
            Auth.isAuthenticated().should.be.false;
        });
    });
    describe('logOut()', function () {
        it('should make a call to the server to log the user out', function () {
            // expect a GET request to be made
            // regex to capture all requests to a certain endpoint regardless of domain.
            httpBackend.expectGET(/https:'/'/.+'/logout/).respond(200);
            // call the logOut method on Auth service
            Auth.logOut();
            // flush to execute defined mock behavior.
            httpBackend.flush();
        });
    });
});

我的问题是以下测试:

describe('isAuthenticated()', function () {
    it('should return false if user is not authenticated', function () {
        Auth.isAuthenticated().should.be.false;
    });
});

根据我的理解，每个"描述"和/或"它"块应该是完全独立的。我认为在每次测试之前注入一个新的Auth实例。但是，由于在此测试运行之前身份验证测试成功，因此上述测试失败。

因此输出变成:

Chrome 33.0.1750 (Mac OS X 10.8.2) Service: Auth isAuthenticated() should return false if user is not authenticated FAILED
    expected true to be false
    AssertionError: expected true to be false

我错过了什么?每次测试后我必须手动重置Auth对象吗?我尝试在afterEach()函数中设置Auth ={}，但这似乎没有改变任何东西。

感谢您花时间阅读这个问题。

更新:

我知道问题所在。在Auth.getCurrentUser()中，我从$window.sessionStorage抓取"currentUser"。因此，我确实获得了Auth的每个测试的新实例(我认为)，但相同的$window实例。sessionStorage正在被使用

问题现在应该是…"我如何清除$window ?"