Ngrx茉莉花大理石测试选择器：预期$ .length = 1等于2

Question

我正在尝试测试一个简单的加载器组件，该组件正在从我制作的ngrx选择器获取其状态。选择器提供了一个对象（接口名称为LoaderState）{queue: number}，我将其映射为一个布尔值以显示或隐藏加载器。

为了对其进行测试，我使用了ngrx的茉莉花大理石和mockStore。我覆盖了选择器，使用期望值创建了一个预期的冷观测值，然后使用期望值进行观测。

我遵循了ngrx doc和Angular Up conf中的教程。

组件

export class LoaderComponent implements OnInit {
  state: Observable<boolean>

  constructor(
    private store: Store<State>
  ) { }

  ngOnInit() {
    this.state = this.store.select(selectLoader).pipe(
      map(state => !!state.queue)
    )
  }

}

规范

describe('LoaderComponent', () => {
  let component: LoaderComponent
  let fixture: ComponentFixture<LoaderComponent>
  let store: MockStore<State>
  let loaderSelector: MemoizedSelector<State, LoaderState>

  beforeEach(async(() => {
    TestBed.configureTestingModule({
      declarations: [ LoaderComponent ],
      providers: [ provideMockStore()]
    }).compileComponents()
    store = TestBed.get(Store)
    loaderSelector = store.overrideSelector(selectLoader, {queue: 0})
  }))

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

  it('should hidden', () => {
    const expected = cold('(a|)', { a: false })
    expect(component.state).toBeObservable(expected)
  })
})

我希望测试能够通过，并且代码也可以正常运行，但是测试失败，并且导致的错误是：

[ { frame: 0,
        notification: { kind: 'N', value: false, error: undefined, hasValue: true } ‍},‍
‍      { frame: 0,‍
‍        notification: { kind: 'C', value: undefined, error: undefined, hasValue: false } ‍} ]
     
    Expected $.length = 1 to equal 2. 
    Expected $[1] = undefined to equal Object({ frame: 0, notification: Notification({ kind: 'C', value: undefined, error: undefined, hasValue: false }) }).