在单元测试中模拟HttpResponse Angular2

在其中一个单元测试中，我需要模拟http响应，我想我是照本宣科地这么做的，但不管出于什么原因，我似乎得到了以下异常：

‘TypeError: Cannot read property 'subscribe' of undefined’

这是关于这一行的：

 mockBackend.connections.subscribe((connection)


describe('ServiceUnderTest', () => {
  beforeEach(() => {
    TestBed.configureTestingModule({
      providers: [ServiceUnderTest, MockBackend, BaseRequestOptions,
        { provide: XHRBackend, useExisting: MockBackend },
        {
          provide: Http,
          deps: [XHRBackend, BaseRequestOptions],
          useFactory: (backend, options) => { return new Http(backend, options); },
        }],
      imports: [HttpModule],
    });
  });

 it('should return array', async(inject([ServiceUnderTest, MockBackend], (service: ServiceUnderTest, mockBackend) => {

    const mockResponse: any = {
      data: [
        { 'code': '123', 'desc': 'ab' },
        { 'code': '345', 'desc': 'cd' },         
      ],
    };

    // Line which throws error
    mockBackend.connections.subscribe((connection) => {
      connection.mockRespond(new Response(new ResponseOptions({
        body: JSON.stringify(mockResponse),
      })));
    });

    service.getMyGear().subscribe(result => {
      let fishingGears: Array<any> = result;
      expect(fishingGears.length).toBe(3);
      expect(fishingGears[0].desc).toBe('Pots');
    });

根据文档属性：mockBackend.connections应该只存在于mock实现中

你知道为什么这个财产不存在吗

---

问候

我发现我通过测试的东西有问题-它实际上是一个空对象

我发现我通过测试的东西有问题-它实际上是一个空对象

mockBackend.http._backend.connections