问在使用jasmine的服务测试中，Spy返回值无法正常工作

EN

export class NetworkService {

  testNumber = 0;

  constructor(private networkReducerService: NetworkReducerService) {
    this.testNumber = networkReducerService.getNumber();
  }
}

describe('NetworkService', () => {

  let service: NetworkService;
  let networkReducerServiceSpy: jasmine.SpyObj<NetworkReducerService>;

  beforeEach(() => {

    const nRServiceSpy = jasmine.createSpyObj('NetworkReducerService', ['getNumber']);

    TestBed.configureTestingModule({
      providers: [NetworkService,
        {provide: NetworkReducerService, useValue: nRServiceSpy}
      ]
    });
    service = TestBed.get(NetworkService);
    networkReducerServiceSpy = TestBed.get(NetworkReducerService);
  });

  it('should have the following fields', () => {

    networkReducerServiceSpy.getNumber.and.returnValue(1);

    expect(networkReducerServiceSpy.getNumber).toHaveBeenCalled();

    expect(service.testNumber).toBe(1);
  });

});

@Injectable({
  providedIn: 'root'
})
export class NetworkReducerService {
  getNumber() {
    return 1;
  }
}