角度测试-如何在ab Observable订阅中测试函数调用？

Question

我有一个Angular组件，它订阅了ngOnInit生命周期挂钩内的Observable。这里还有其他事情在起作用，例如NgRx商店，但这与这个问题无关。因此，相关代码：

...
ngOnInit() {
  this.loginForm = this.formBuilder.group({
    usernameOrEmail: ['', [Validators.required]],
    password: ['', [Validators.required]]
  });

  this.authenticating$ = this.store.pipe(select(selectUserAuthenticating));
  this.authenticating$
    .pipe(takeUntil(this.destroy$))
    .subscribe(authenticating =>
      // This is the relevant part
      authenticating ? this.loginForm.disable() : this.loginForm.enable()
    );
}
...

现在，我想测试在this.loginForm.disable()可观察的订阅中是否正在调用this.loginForm.enable()或authenticating$。

我已经使用RxJs TestScheduler和大理石语法对异步Observable进行测试，从而进行了这样的测试：

...
import { TestScheduler } from 'rxjs/testing';
...

describe('LoginComponent', () => {

  ...

  beforeEach(async(() => {
    let scheduler: TestScheduler;
    ...
  });

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

  beforeEach(() => {
    scheduler = new TestScheduler((actual, expected) => {
      expect(actual).toEqual(expected);
    });
  });

  it('should disable the form while the user is authenticating', () => {
    const formDisableSpy = jest.spyOn(component.loginForm, 'disable');

    scheduler.run(({ hot, expectObservable }) => {
      component.authenticating$ = hot('-a', { a: true });
       expectObservable(component.authenticating$).toBe('-b', { b: true });
    });

    component.authenticating$.subscribe(authenticating => {
      expect(authenticating).toBe(true);
      expect(formDisableSpy).toHaveBeenCalled();
    });
  });
});

但是，测试结果表明从未调用过函数this.loginForm.disable()。但是，authenticating的值已正确测试。查看Jest测试的控制台输出：

Expected mock function to have been called, but it was not called.

                    expect(authenticating).toBe(false);
    > 133 |         expect(component.loginForm.enable).toHaveBeenCalled();
          |                                            ^

问题

如何在Angular组件的Observable订阅中测试函数调用？