javascript - 使用 angular/karma/jasmine 模拟异步服务功能

Question

这段代码中的测试没有成功。我似乎无法成功测试异步函数的返回。

describe('mocking services', function () {

    var someService, deferred;

    beforeEach(function () {

        module(function($provide){
            $provide.factory('someService', function($q){
                return{
                    trySynch: function(){
                        return 33;
                    },
                    tryAsynch: function(){
                        deferred = $q.defer();
                        return deferred.promise;
                    }
                };
            });
        });

        inject(function (_someService_) {
            someService = _someService_;
        });
    });

    it('should be able to test values from both functions', function () {
        expect(someService.trySynch()).toEqual(33);

        var retVal;
        someService.tryAsynch().then(function(r){
            retVal = r;
        });
        deferred.resolve(44);
        expect(retVal).toEqual(44);
    });

});

当我运行它时，出现以下错误:

Chrome 36.0.1985 (Mac OS X 10.9.4) mocking services should be able to test values from both functions FAILED
        Expected undefined to equal 44.
        Error: Expected undefined to equal 44.
            at null.<anonymous> (/Users/selah/WebstormProjects/macrosim-angular/test/spec/services/usersAndRoles-service-test.js:34:24)

我怎样才能通过这个测试？

Answer 1

当使用 $q 模拟异步调用时，由于 $q 的实现方式，您需要使用 $rootScope.$apply()。

具体来说，.then 方法不会被同步调用，它被设计为始终是异步的，无论它是如何被调用的——同步或异步。

为实现这一点，$q 与 $rootScope 集成在一起。因此，在您的单元测试中，您需要通知 $rootScope 某些内容已更改(即 - 触发摘要循环)。为此，您调用 $rootScope.$apply()

参见 here (specifically the "Differences between Kris Kowal's Q and $q section")

工作代码如下所示:

describe('mocking services', function () {

    var someService, deferred, rootScope;

    beforeEach(function () {

        module(function($provide){
            $provide.factory('someService', function($q){
                return{
                    trySynch: function(){
                        return 33;
                    },
                    tryAsynch: function(){
                        deferred = $q.defer();
                        return deferred.promise;
                    }
                };
            });
        });

        inject(function ($injector) {
            someService = $injector.get('someService');
            rootScope = $injector.get('$rootScope');
        });
    });

    it('should be able to test values from both functions', function () {
        expect(someService.trySynch()).toEqual(33);

        var retVal;
        someService.tryAsynch().then(function(r){
            retVal = r;
        });
        deferred.resolve(44);
        rootScope.$apply();
        expect(retVal).toEqual(44);
    });

});