目标

you have to create the DOM elements associated with the components, you must examine the DOM to confirm that component state displays properly at the appropriate times, and you must simulate user interaction with the screen to determine whether those interactions cause the component to behave as expected.

一个例子：

describe('BannerComponent (with beforeEach)', () => {
  let component: BannerComponent;
  let fixture: ComponentFixture<BannerComponent>;

  beforeEach(() => {
    TestBed.configureTestingModule({declarations: [BannerComponent]});
    fixture = TestBed.createComponent(BannerComponent);
    component = fixture.componentInstance;
  });

  it('should create', () => {
    expect(component).toBeDefined();
  });
});

it('should contain "banner works!"', () => {
  const bannerElement: HTMLElement = fixture.nativeElement;
  expect(bannerElement.textContent).toContain('banner works!');
});

如果是在浏览器环境下运行，可以使用常规的DOM操作API访问htnl元素：

it('should have <p> with "banner works!"', () => {
  const bannerElement: HTMLElement = fixture.nativeElement;
  const p = bannerElement.querySelector('p');
  expect(p.textContent).toEqual('banner works!');
});

Angular Component的DOM单元测试

目标