angular - 在 Angular/Jasmine 单元测试中绕过 *ngIf

Question

仅供引用，在 github 上记录了一个问题，还在错误中包含了 plunkr 的详细信息:https://github.com/angular/angular/issues/19292

我根本无法通过 ngIf 来检查值。如果我删除 ngIf 它工作正常。为了尝试解决这个问题，我直接在 beforeEach() 中硬编码了大使的值。但无济于事，我错过了其他东西。

在 HTML 中:

 <h3 class="welcome" *ngIf="ambassador"><i>{{ambassador.username}}</i></h3>

Jasmine :

beforeEach(() => {

    TestBed.configureTestingModule({
       declarations: [ ProfileComponent, BannedComponent ],
       providers:    [ HttpClient, {provide: AmbassadorService, useClass: MockAmbassadorService } ],
       imports:      [ RouterTestingModule, FormsModule, HttpClientModule ]
    });

    fixture = TestBed.createComponent(ProfileComponent);
    component    = fixture.componentInstance;

    // AmbassadorService actually injected into the component
    ambassadorService = fixture.debugElement.injector.get(AmbassadorService);
    componentUserService = ambassadorService;
    // AmbassadorService from the root injector
    ambassadorService = TestBed.get(AmbassadorService);

    // set route params
    component.route.params = Observable.of({ username: 'jrmcdona' });
    component.ambassador = new Ambassador('41', '41a', 'jrmcdona', 4586235, false);
    component.ngOnInit();
  });

  it('should search for an ambassador based off route param OnInit', () => {
     de = fixture.debugElement.query(By.css('.welcome'));
    el = de.nativeElement;
    fixture.detectChanges();
    const content = el.textContent;
    expect(content).toContain('jrmcdona', 'expected name');
  });

Answer 1

问题是 DOM 在您手动检测更改之前不会更新，并且您试图在 *ngIf 呈现之前查询 DOM(并且 ambassador 值为检测到)。

  it('should search for an ambassador based off route param OnInit', () => {
    fixture.detectChanges();
     de = fixture.debugElement.query(By.css('.welcome'));
    el = de.nativeElement;
    const content = el.textContent;
    expect(content).toContain('jrmcdona', 'expected name');
  });

将 detectChanges() 移动到 query() 之前应该可以解决问题。