如何测试是否以角度呼叫用户？

Question

我有一个组件正在订阅由服务创建的全局扇出，并且我想测试扇出是否确实被正确接收。因此，请看下面的代码，我想测试是否在TestableComponent中调用了eventStartFanout $。

我知道代码实际上是通过做“手动测试”来工作的，=用我的眼睛，但是我不知道如何将其转换为自动测试。

我当前问题的最小示例；

服务：

eventStartSubject = new Subject<any>();
eventStartFanout$ = this.eventStartSubject.asObservable();
function startEvent() {
  this.eventStartSubject.next();
}

testable-component：

ngOnInit() {
  this.unchanged = true;
  this.fanoutService.eventStartFanout$.subscribe(
    _ => {
      // Test that it reaches here when service triggers
      this.changeVariable();
    }
  );
}

// Extra (unneeded) function to potentially help testing
function changeVariable(){
  this.unchanged = false;
}

我当前的测试尝试：

beforeEach(() => {
    fixture = TestBed.createComponent(TestableComponent);
    component = fixture.componentInstance;
    fixture.detectChanges();
  });

it('should do something when fanout happens', async(() => {
    const fanoutService: FanoutService = TestBed.get(FanoutService);
    component.unchanged = true;
    spyOn(component, 'changeVariable');
    // It should trigger the subscriber here and change component.unchanged
    fanoutService.startEvent();
    fixture.detectChanges();
    expect(component.unchanged).toBeFalsy();
  }));

Answer 1

比我想的要简单。解决方案是使用fakeAsync和tick()模拟订户可以执行更改的时间步，请参阅：

it('should do something when fanout happens', fakeAsync(() => {
    const fanoutService: FanoutService = TestBed.get(FanoutService);
    component.unchanged = true;
    fanoutService.startEvent();
    tick();
    fixture.detectChanges();
    expect(component.unchanged).toBeFalsy();
  }));