如何测试ngOnInit生命周期中的可观察性？

import { ComponentFixture, TestBed } from '@angular/core/testing';
import { MyComponent } from './my.component';
import { Observable, of } from 'rxjs';
import { TestScheduler } from 'rxjs/testing';

describe('MyComponent', () => {
  let component: MyComponent;
  let fixture: ComponentFixture<MyComponent>;
  let scheduler: TestScheduler;

  beforeEach(async () => {
    await TestBed.configureTestingModule({
      declarations: [MyComponent],
    }).compileComponents();
  });

  beforeEach(() => {
    fixture = TestBed.createComponent(MyComponent);
    component = fixture.componentInstance;
    scheduler = new TestScheduler((actual, expected) => {
      expect(actual).toEqual(expected);
    });
  });

  it('should subscribe and unsubscribe from observable in ngOnInit', () => {
    const observable = of('test');
    const subscribeSpy = spyOn(observable, 'subscribe');

    scheduler.run(({ expectObservable }) => {
      component.ngOnInit();
      expect(subscribeSpy).toHaveBeenCalled();

      expectObservable(observable).toBe('(x|)', { x: 'test' });

      component.ngOnDestroy();
      expect(subscribeSpy).toHaveBeenCalledTimes(1);
    });
  });
});