如何在API失败时对ngrx效果进行单元测试？

import { TestBed } from '@angular/core/testing';
import { provideMockStore, MockStore } from '@ngrx/store/testing';
import { provideMockActions } from '@ngrx/effects/testing';
import { Observable, throwError } from 'rxjs';
import { cold, hot } from 'jasmine-marbles';

import { MyEffects } from './my-effects';
import { MyService } from './my-service';
import { MyActionTypes, MyAction } from './my-actions';

describe('MyEffects', () => {
  let effects: MyEffects;
  let actions$: Observable<any>;
  let store: MockStore;
  let myService: jasmine.SpyObj<MyService>;

  beforeEach(() => {
    const spy = jasmine.createSpyObj('MyService', ['apiCall']);
    TestBed.configureTestingModule({
      providers: [
        MyEffects,
        provideMockActions(() => actions$),
        provideMockStore(),
        { provide: MyService, useValue: spy }
      ]
    });

    effects = TestBed.inject(MyEffects);
    actions$ = TestBed.inject(Actions);
    store = TestBed.inject(MockStore);
    myService = TestBed.inject(MyService) as jasmine.SpyObj<MyService>;
  });

  it('should dispatch MyFailureAction when API call fails', () => {
    const error = new Error('API call failed');
    myService.apiCall.and.returnValue(throwError(error));

    const action = new MyAction();
    actions$ = hot('-a', { a: action });
    const expected = cold('-b', { b: new MyFailureAction(error) });

    expect(effects.myEffect$).toBeObservable(expected);
  });
});