Jasmine和angularjs,在茉莉花中使用$cookies

我在apps.js中创建了一个全局命名空间’cp’,并在服务和控制器中使用它.

//controller
cp.controller = {};
cp.controller.LoginController = function($scope,$location,$cookies){
        $scope.signIn = function(){
            $cookies.user = $scope.form.username;
            user.set($scope.form.username);
            $location.hash( "home" );
        }
};
//service 
cp.serviceFactory = {};
cp.serviceFactory.user = function user( $cookies){
    var userName = $cookies.user;
    return{
        set: function(name){
            userName = name;
        },get: function(){
            return userName;
        }
    }
};
//test script
describe('Cameo Controllers',function() {

    describe('LoginController',function(){
        var scope,cookies,ctrl,$httpBackend;
        beforeEach(module('CameoPaaS'));
        beforeEach(inject(function(_$httpBackend_,$rootScope,$controller,$cookies) {
            $httpBackend = _$httpBackend_;
           // cookies =  $cookies.username;
            scope = $rootScope.$new();
            cookies = scope.$cookies;
            ctrl = $controller(cp.controller.LoginController,{$scope: scope,$cookies: cookies});
        }));
        it('should log the user into the system',function() {
            expect(scope.username).toBeUndefined();
            scope.form.username = 'me';
            scope.signIn();
            //expect(user).toBe(undefined);
        });
    });
});

问题：如何在测试脚本中定义和设置$cookies.username的值以解决错误.