Testing Data Services

Spector makes testing data services, which use the Angular HTTP module, a lot easier. For example, let's say that you have a data service with two methods, one performes a GET and one a POST.

export class TodosDataService {
  constructor(private http) {}

  get() {
    return this.http.get('todos');
  }

  post(id: number) {
    return this.http.post('todos', { id });
  }
}

import { TodosDataService } from './todos-data.service';
import { createHTTPFactory, HTTPMethod } from '@netbasal/spectator';

describe('HttpClient testing', () => {
  let http = createHTTPFactory<TodosDataService>(TodosDataService);

  it('can test HttpClient.get', () => {
    let { dataService, controller, expectOne } = http();

    dataService.get().subscribe();
    expectOne('todos', HTTPMethod.GET);
  });

  it('can test HttpClient.post', () => {
    let { dataService, controller, expectOne } = http();

    dataService.post(1).subscribe();

    const req = expectOne('todos', HTTPMethod.POST);
    expect(req.request.body['id']).toEqual(1);

  });
});

First, you need to create an HTTP factory by using the createHTTPFactory() function, passing the data service that you want to test.

The createHTTPFactory() returns a function which can be called to get an instance of SpectatorHTTP with the following properties:

• controller - A proxy for Angular HttpTestingController
• httpClient - A proxy for Angular HttpClient
• dataService - The data service instance (todosService)
• get<T> - A proxy for Angular TestBed.get()

One useful method is expectOne() which lets to expect that a single request was made which matches the given URL and it's method, and return its mock request. expectOne(url: string, method: HTTPMethod) => TestRequest

  it("should work with external service", fakeAsync(() => {
      let { dataService, controller, expectOne, get } = http();
      get(UserService).getUser.andCallFake(() => {
        return defer(() => Promise.resolve({}));
      });

      const req = dataService.requestWithExternalService().subscribe();
      tick();

      expectOne("two", HTTPMethod.GET);
    })
  );