我开始在 Angular 中测试组件和服务。我观看了 pluralsight 上的课程，并尝试遵循以下想法： https://codecraft.tv/courses/angular/unit-testing/mocks-and-spies/ 但是，我在测试组件方法方面遇到了问题。不幸的是，我找不到解决方案，所以决定向您寻求帮助。

我的服务：

@Injectable()
export class MyService {
  private config: AppConfig;
  constructor(private apiService: ApiService, private configService: ConfigurationService) {
    this.config = configService.instant<AppConfig>();
  }

  public get(name: string, take: number = 10, skip: number = 0, params?:any): Observable<any> {
    return this.apiService.post(`${this.config.baseUrl}/${name}/paginated?take=${take}&skip=${skip}`, params);
  }
}

我的组件：

 @Component({
  selector: 'my',
  templateUrl: './my.component.html',
  styleUrls: ['./my.component.scss']
})
export class MyComponent implements OnInit {
  @Input("customerId") customerId: string;
  items: CustomerItem[] = [];

  public pagingInfo: PagingMetadata = {
    itemsPerPage: 5,
    currentPage: 1,
    totalItems: 0
  };
  constructor(private service: MyService) { }

  ngOnInit() {
    if (this.customerId) {
      this.updateItems();
    }
  }

  updateItems() {
    let skip = (this.pagingInfo.currentPage - 1) * this.pagingInfo.itemsPerPage;
    let take = this.pagingInfo.itemsPerPage;
    this.service.get("customer", take, skip, { customerId: this.customerId }).subscribe(result => {
      this.items = result.entities;
      this.pagingInfo.totalItems = result.total;
    }, (error) => {
      console.log(error.message);
    });
  }
}

我的 my.component.spec.ts 测试文件：

describe('MyComponent', () => {
  let component: MyComponent;
  let fixture: ComponentFixture<MyComponent>;
  let mockService;
  let ITEMS = [
    {
        "title": "test",
        "id": "5e188d4f-5678-461b-8095-5dcffec0855a"
    },
    {
        "title": "test2",
        "id": "5e188d4f-1234-461b-8095-5dcffec0855a"
    }
]

beforeEach(async(() => {
  mockService = jasmine.createSpyObj(['get']);

  TestBed.configureTestingModule({
    imports: [NgxPaginationModule, RouterTestingModule],
    declarations: [MyComponent],
    providers: [
      { provide: MyService, useValue: mockService }
    ]
  })
    .compileComponents();
}));

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

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

// works fine
it('should NOT call updateItems method on initialization', () => {
  component.ngOnInit();
  let spy = spyOn(component, 'updateItems').and.callThrough();

  expect(spy).not.toHaveBeenCalled();
});

// works fine
it('should call updateItems method on initialization', () => {
    component.customerId = "1";
    let spy = spyOn(component, 'updateItems').and.callFake(() => { return null });

    component.ngOnInit();

    expect(spy).toHaveBeenCalled();
  });

// gives error
it('should update items', () => {
  component.pagingInfo.currentPage = 1;
  component.pagingInfo.itemsPerPage = 10;
  component.customerId = "1";
  mockService.get.and.returnValue(of(ITEMS));

  component.updateItems();

  expect(component.items).toBe(ITEMS);
});
});

前 3 个测试工作正常，但是最后更新项目时出现错误：

Expected undefined to be [ Object({"title": "test","id": "5e188d4f-5678-461b-8095-5dcffec0855a"},{"title": "test2","id": "5e188d4f-1234-461b-8095-5dcffec0855a"})]

如能提供任何提示，我将不胜感激 ;)