带有 setTimeOut 的 Angular 6 单元测试 ngOnInit 不起作用

Question

我在 ngOnInit 函数中有一个带有 setTimeOut 函数的组件。要为此编写单元测试用例，我使用 tick 和 fakeAsync 来快进 setTimeOut。但是，它不会被执行，而不会调用其他函数 closeAlert()。

组件代码：

export class BannerComponent implements OnInit {

  @Input()errorData: any;

  @Input()callback: any;

  @Input()autoHide: boolean;

  constructor() { }

  ngOnInit() {

    if (this.autoHide) {
      setTimeout
        (() => {
          this.closeAlert();
        }, 500);
    }
  }

  closeAlert() {
    this.errorData = null;
    if (this.callback) {
      this.callback();
    }
  };
}

规范文件：

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

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

  beforeEach(async() => {
    fixture = TestBed.createComponent(BannerComponent);
    component = fixture.componentInstance;
    component.ngOnInit();
    fixture.detectChanges();
  });

  it("banner should hide after 500ms", fakeAsync(() => {
    component.errorData = {
      _statusMessage: "New alert banner",
      _statusCode: '200',
    };
    component.callback = null;;
    component.autoHide = true;

    tick(600);
    fixture.detectChanges()

    fixture.whenStable().then(() => {
      let banner = fixture.debugElement.query(By.css('.success'));
      expect(banner).toBe(null)
    })
  }));

});

html代码：

<div class="success">
    <p>{{errorData._statusMessage}}</p>
</div>

Answer 1

我在代码中看到了几个问题。

• 您呼叫都component.ngOnInit()和fixture.detectChanges()（也称之为ngOnInit）之前，您已经在建立有效的数据component.errorData。
• 我不清楚为什么您希望banner显示的 html 为空。因此，我将测试更改为查看component.closeAlert()已调用，如果component.errorData已重置为空，因为这似乎是您真正想要测试的内容。为了测试这一点，我监视了component.closeAlert().
• 我设置了刻度，以component.closeAlert()通过测试 after来准确显示调用的时间tick(499)，然后再经过一个刻度......

工作StackBlitz。

代码：

beforeEach(async(() => { // slight correction of incorrect async wrapper ...
  fixture = TestBed.createComponent(BannerComponent);
  component = fixture.componentInstance;
  // component.ngOnInit(); // <-- don't call this here, the data isn't set up yet ...
  // fixture.detectChanges(); // ditto
}));

it("banner should hide after 500ms", fakeAsync(() => {
  spyOn(component, 'closeAlert').and.callThrough(); // set up a spy so we can test later
  component.errorData = {
    _statusMessage: "New alert banner",
    _statusCode: '200',
  };
  component.callback = null;;
  component.autoHide = true;

  fixture.detectChanges(); // <-- this will execute ngOnInit()
  expect(component.errorData).not.toBeNull(); // <-- after ngOnInit, still NOT null
  expect(component.closeAlert).not.toHaveBeenCalled();
  tick(499); // <-- now let 499ms pass ...
  expect(component.errorData).not.toBeNull(); // <-- after all that "fake" time, still NOT null
  expect(component.closeAlert).not.toHaveBeenCalled();
  tick(1); // <-- now tick for just 1 more millisecond ...
  expect(component.errorData).toBeNull(); // <-- now this has become NULL
  expect(component.closeAlert).toHaveBeenCalled(); // <-- and the method was called
  // fixture.whenStable().then(() => {
  //   let banner = fixture.debugElement.query(By.css('.success'));
  //   expect(banner).toBe(null)
  // });
}));

我希望这有帮助！