使用Angular 7进行单元测试

Question

I am trying to write unit test for this angular script:

export class DataService {
  private csrfToken: string = '';

  private isContentShow: BehaviorSubject<boolean> = new BehaviorSubject(true);

  constructor(private http: HttpClient, private cookieService: CookieService) {
    this.token = this.cookieService.get('token');
  }

  public createData(data: Data) {
    try {
       this.http.post(  url,
                        data,
                        {
                          headers: new HttpHeaders({
                              'Content-Type':  'application/json',
                              'Authorization': this.token
                          })
                        })
      .subscribe(
        data => {
                this.isContentShow.next(true);
                },
        err => {
        this.showError();
        },
        () => console.log('Request Complete')
      );
      return true;
    } catch {
      this.showError();
      }
    }

  public getIsContentShow(): Observable<boolean> {
    return this.isContentShow.asObservable();
  } 
}

The test that I had so far and its running as expected.

 it('#getIsContentShow should return value from observable',
    (done: DoneFn) => {
    service.getIsContentShow().subscribe(value => {
      expect(value).toBe(true);
      done();
    });
  });

However I am trying to write the test for createData() function

I am able to mock the HttpClient using HttpClientTestingModule however I don't know how to handdle the CookieService and token ?

Thanks

Answer 1

You can use spies to spy on the cookieService get method. This way, you can write your unit test to test the combinations of returns you say the cookieService can provide.

This link says that you can spy on the prototype of the method in order to handle it how you like in the constructor.

it(
  "should call #getGeneralStats in the constructor",
  inject(
    [CookieService, HttpClient],
    (cookieService: CookieService, http: HttpClient) => {
      let mySpy = spyOn(cookieService, 'get').and.returnValue(<your value>);

      dataService = new DataService(http, cookieService);

      expect(mySpy).toHaveBeenCalled();
    }
  )
);

For you, this may depend on how you're writing your tests. The example shows the service being instantiated like new ServiceName , but it's also possible to use dependency injection to get the service. If you're using DI for the service you are testing, I'd have to research more how to do this (others please feel free to add your answer if you know how to do that)!