我目前正在处理一个Angular项目，并且正在使用Karma + Jasmine为一个组件创建单元测试，因此我有一个HTML，其中包含一个ngIf，调用API服务如下：

• • 超文本标记语言**

<div class="row" *ngIf="apiService.utilsService.userBelongsTo('operations')"></div">

*ngIf中的服务就是我想要在下面的spec.ts上模拟的服务

• • 技术支助**

export class CashFlowSalariesComponent implements OnInit, OnChanges {
constructor(
public apiService: ApiService,
) {}

• • SPECT. TS**

describe('CashFlowSalariesComponent', () => {
      let fixture: ComponentFixture < CashFlowSalariesComponent > ;
      let mockApiService;
      let data;

      beforeEach(async(() => {
        data = [{
          id: 1006,
          role: "Developer",
          ...
        }]

        mockApiService = jasmine.createSpyObj(['userBelongsTo'])

        TestBed.configureTestingModule({
          schemas: [CUSTOM_ELEMENTS_SCHEMA],
          imports: [
            RouterTestingModule,
            FormsModule,
            ReactiveFormsModule,
            BrowserModule,
            HttpClientTestingModule,
            ToastrModule.forRoot({
              positionClass: 'toast-bottom-right'
            })
          ],
          declarations: [
            CashFlowSalariesComponent,
          ],
          providers: [{
              provide: ApiService,
              useValue: mockApiService
            }, UserService, ProfileService, VettingStatusService, ApplicationRoleService,
            SeniorityLevelService, PlacementStatusService, EducationLevelService, UtilsService, ShirtSizeService,
            CountryService, CityService, PostalCodeService, StateService, ClientSectorService, JobService, ProfileActivityService, ProfileSalaryActivityService, ClientService, RequestTimeOffService, TimeOffTypeService, PulsecheckDetailService, PulsecheckMasterService,
            PulsecheckQuestionService, ExpenseService, DepartmentService, ExchangeRateService, SkillCategoriesService, ProfileRoleService,
            ToastrService
          ]

        })

        fixture = TestBed.createComponent(CashFlowSalariesComponent);
      }));

      it('should set salaries data correctly', () => {
        mockApiService.userBelongsTo.and.returnValue(of('operations'))
        debugger;
        fixture.detectChanges();
      })

如您所见，我尝试创建API服务的模拟：mockApiService = jasmine.createSpyObj(['userBelongsTo'])，则在it中使用：mockApiService.userBelongsTo.and.returnValue(of('operations'))，但是当我调试它时，它抛出如下图所示的未知

测试返回以下错误：
无法读取未定义的属性（读取"userBelongsTo"）
我不知道发生这种情况是否是因为userBelongs属于apiService中的另一个服务：

• • Api服务**

@Injectable()
export class ApiService {
 public utilsService: UtilsService;

constructor(private injector: Injector) {
this.utilsService = injector.get(UtilsService);
}
}

• • 实用程序服务：**

userBelongsTo(groupName: string) {
    return this.groups.split(',').reduce((c, g) => c || g.toUpperCase() == groupName.toUpperCase(), false);
  }

我怎样才能让这个工作？