Angular 单元测试 ngOnInit 订阅

Question

我开始使用 Jasmine 在 Angular 9 中进行单元测试。

我正在测试一个实现 ngOnInit:

的简单组件

export class HomeComponent implements OnInit {

      constructor(private router: Router
        , private authenticationService: AuthenticationService) { }

        ngOnInit(): void {
        this.authenticationService.checkIsAuthenticatedObservable()
        .subscribe(
          (isAuthenicated: boolean) => {
            if (isAuthenicated === true) {
              this.router.navigate(['/observation-feed']);
            }
          });
        }
      }

我在执行 ngOnInIt 生命周期挂钩时遇到错误：

TypeError: Cannot read property 'subscribe' of undefined
    at <Jasmine>
    at HomeComponent.ngOnInit (http://localhost:9876/_karma_webpack_/main.js:8140:13)

我的测试规范是这样设置的：

describe('HomeComponent', () => {
  let component: HomeComponent;
  let fixture: ComponentFixture<HomeComponent>;
  let router: Router;
  let mockAuthenticationService;

  beforeEach(async(() => {
    mockAuthenticationService = jasmine.createSpyObj(['checkIsAuthenticatedObservable']);

    TestBed.configureTestingModule({
      imports: [
        RouterTestingModule.withRoutes([
          // { path: 'login', component: DummyLoginLayoutComponent },
        ])
      ],
      declarations: [ HomeComponent ],
      providers: [
        { provide: AuthenticationService, useValue: mockAuthenticationService }
      ]
    })
    .compileComponents();
  }));

  beforeEach(() => {
    fixture = TestBed.createComponent(HomeComponent);
    router = TestBed.get(Router);
    component = fixture.componentInstance;
    fixture.detectChanges();
  });

  it('should create', () => {
    mockAuthenticationService.checkIsAuthenticatedObservable.and.returnValue(of(false));
    fixture.detectChanges();
    // component.ngOnInit();

    expect(component).toBeTruthy();
  });
});

我尝试了设置模拟对象的各种组合，并在初始化的不同点调用 fixture.detectChanges(); 和 component.ngOnInit();。 None 我尝试过的方法都有效。这里出了什么问题？

Answer 1

当您在 beforeEach 部分调用 fixture.detectChanges 时，Angular 运行生命周期挂钩并调用 ngOnInit。这就是为什么你会出错 - 你在测试中模拟 checkIsAuthenticatedObservable，在第一个 fixture.detectChanges 之后。将模拟移动到 beforeEach 部分，在 fixture.detectChanges 之前，它将正常工作。此外，对于 Angular 9，您应该使用 TestBed.inject 而不是现在已弃用的 TestBed.get。

beforeEach(() => {
    fixture = TestBed.createComponent(HomeComponent);
    router = TestBed.inject(Router);
    component = fixture.componentInstance;
    mockAuthenticationService.checkIsAuthenticatedObservable.and.returnValue(of(false));
    fixture.detectChanges();
  });

  it('should create', () => {
    fixture.detectChanges();
    expect(component).toBeTruthy();
  });

Angular 单元测试 ngOnInit 订阅

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