TypeError: Cannot read property 'token' of null

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 have tried this code to test my service. In this post I want to know, How to test this service CityService

describe('Service: City', () => {
let service: CityService;

beforeEach(() => {
TestBed.configureTestingModule({
declarations: [],
providers: [CityService, AuthService, Http, ConnectionBackend],
imports: [RouterTestingModule, HttpClientTestingModule, HttpModule]
});
});

beforeEach(() => {
service = TestBed.get(CityService);
});

it('#getAllCity should return real value', () => {
expect(service.getAllCity()).toBe('real value');
});
});


I tried this code, but show me error:

TypeError: Cannot read property 'token' of null
​

How to test / how to show my city in ng test?

This is my first attempt, can you suggest me any example, or tutorial like my code?

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