How to test my service function using Typescript, Angular5

I have this service that return all City from ws.

@Injectable()
export class CityService {
  constructor(private http: Http, private router: Router,
  private auth: AuthService) { }

  public getAllCity(): Observable<City[]> {
    let headers = new Headers();
    headers.append('x-access-token', this.auth.getCurrentUser().token);
    return this.http.get(Api.getUrl(Api.URLS.getAllCity), {
      headers: headers
    })
      .map((response: Response) => {
        let res = response.json();
        if (res.StatusCode === 1) {
          this.auth.logout();
        } else {
          return res.StatusDescription.map(city => {
            return new City(city);
          });
        }
      });
  }
}

Now, I want to test this ws, I tried this code:

describe('Service: City', () => {
    let component: CityService;
    let fixture: ComponentFixture<CityService>;

    beforeEach(() => {
        TestBed.configureTestingModule({
            declarations: [],
            providers: [CityService] 
        })
        fixture = TestBed.get(CityService);
        component = fixture.componentInstance;
    });
});

Please, can you suggest me, how to test, how to show my city in ng test ? Also, please, this is my first work, can you suggest me any example, or tutorial like my code? Thanx