如何在 angular 7 中对 getCurrentNavigation().extras.state 进行单元测试

Question

我正在尝试使用 jasmine 为 getCurrentNavigation().extras.state 编写单元测试。

为了解决这个问题，我试图监视这个路由器方法。

我的组件文件，

@Component({
  selector: 'app-location-list',
  templateUrl: './location-list.component.html',
  styleUrls: ['./location-list.component.scss']
})
export class LocationListComponent implements OnInit{

  locationId;
  locationName;
  constructor(private activatedRoute: ActivatedRoute, private router: Router) {
    if (this.router.getCurrentNavigation().extras.state) {
      this.locationId = this.router.getCurrentNavigation().extras.state.locationId;
    }
    if (this.router.getCurrentNavigation().extras.state) {
      this.locationName = this.router.getCurrentNavigation().extras.state.locationName;
    }
  }
  ngOnInit() { }
}

我的规格文件，

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

  beforeEach(async(() => {
    TestBed.configureTestingModule({
      imports: [
        RouterTestingModule
      ],
      declarations: [
        LocationListComponent 
      ],
      providers: []
    })
      .compileComponents();
  }));

  beforeEach(() => {
    fixture = TestBed.createComponent(LocationListComponent );
    component = fixture.componentInstance;
    spyOn(Router.prototype, 'getCurrentNavigation').and.returnValues({ 'extras': { 'state': { 'locationId': 100, 'locationName': "UK" } } });
    fixture.detectChanges();
  });

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

但我收到以下错误，

TypeError: Cannot read property 'extras' of null

谁能帮我解决这个问题。我正在使用Angular 7.2

Answer 1

您可以使用stub&轻松完成它useClass，spec如果您可以在单独的文件中创建它，它也可以在其他文件中重复使用，然后export class RouterStub尝试：

在spec文件中创建一个stub与以下相同的方法Router：

class RouterStub{
 getCurrentNavigation(){
   return {
      extras: {
         state:{
           locationId: 'someId',
           locationName: 'someName'
         }
       }
     }
   }
}

并在beforeEach()块中：

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

  beforeEach(async(() => {
    TestBed.configureTestingModule({
      imports: [
        RouterTestingModule
      ],
      declarations: [
        LocationListComponent 
      ],
      providers: [ {provide: Router, useClass: RouterStub}]
    })
      .compileComponents();
  }));

  beforeEach(() => {
    fixture = TestBed.createComponent(LocationListComponent );
    component = fixture.componentInstance;
    fixture.detectChanges();
  });

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

Answer 2

如果我们尝试同时使用两者RouterTestingModule，{provide: Router, useClass: RouterStub}它会抛出错误cannot read property 'root' of undefined

所以我们可以直接为Route创建spy并返回它的值

describe('LocationListComponent', () => {
  let component: LocationListComponent ;
  let fixture: ComponentFixture<LocationListComponent>;
  let router: jasmine.SpyObj<Router>;

  beforeEach(async(() => {
    TestBed.configureTestingModule({
      imports: [
        RouterTestingModule
      ],
      declarations: [
        LocationListComponent 
      ],
    })
      .compileComponents();
  }));

  beforeEach(() => {
    router = TestBed.get(Router);
    spyOn(router, 'getCurrentNavigation').and.returnValue({ extras: { state: { message: 'msg'} } } as any);
    fixture = TestBed.createComponent(LocationListComponent);
    component = fixture.componentInstance;
    fixture.detectChanges();
  });

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