Расширение макета не работает, как хотелось бы

Question

Я написал модульный тест для проверки метода с измененным значением. Мне нужно оценить остальную часть IsNotNullOrUndefined (event.value). Я попытался переопределить возвращаемое значение службы, как показано в тесте, отмеченном как подходящий. Тест не пройден с ошибкой. Похоже, расширение не переопределяет его должным образом. Может кто-нибудь сказать мне, в чем может быть проблема

Expected [ Object({ name: 'EVP', version: '2.0.0.0', issued: Date(Wed Apr 22 2020 17:35:38 GMT+0100 (British Summer Time)), deferred: 'Yes (142)', acceptance: '3 d', updated: 
Date(Wed Apr 22 2020 17:35:38 GMT+0100 (British Summer Time)), id: 23 }) ] to be null.

TestComponent

describe('MyAgreementsComponent', () => {
  let component: MyAgreementsComponent;
  let fixture: ComponentFixture<MyAgreementsComponent>;
  let mockAgreementsService: Mock<AgreementsService>;
  const agreementModelObject = AgreementIssuedModelObjectMock;
  const agreementHistoryModel = AgreementHistoryModelMock;

  const setupComponent = () => {
    fixture = TestBed.createComponent(MyAgreementsComponent);
    component = fixture.componentInstance;

    fixture.detectChanges();
  };


  beforeEach(() => {
    mockAgreementsService = new Mock<AgreementsService>({
    getAgreement: () => of(agreementModelObject),
    getAgreementsHistory: () => of(agreementHistoryModel),
  });
  setupComponent();
});

  configureTestSuite(() => {
    TestBed.configureTestingModule({
      imports: [  DevExpressModule,
                  DxDataGridModule,
                  DxButtonModule],
      declarations: [MyAgreementsComponent, MockComponent(SpinnerComponent)],
      providers: [
        { provide: AgreementsService, useFactory: () =>   mockAgreementsService.Object },
        // { provide: Router, useValue:  mockRouter },
        { provide: Router, useClass:  MockHasRouteRouter },
        { provide: ActivatedRoute, useClass: MockActivatedRoute }

      ]
    });
  });



  it('should create', () => {
    expect(component).toBeTruthy();
  });

  describe('#onValueChanged', () => {

    fit('should not filter agreements  when onValueChanged is called with no argument', () => {
     mockAgreementsService.extend({ getAgreementsHistory: () => of(null) });
     fixture.detectChanges();
      component.onValueChanged({ event: null  , value: null });
      expect(component.agreementsHistory).toBeNull();
    });


    it('should filter agreements that are complete when onValueChanged is called with a true event', () => {
      component.agreementsHistoryData = _.cloneDeep(AgreementHistoryModelMock);
      component.onValueChanged({ event: true  , value: true });
      expect(component.agreementsHistory[0].acceptance).toEqual('N/A');
    });

    it('should filter  agreements that are not complete when onValueChanged is called with a true event', () => {
      component.agreementsHistoryData = _.cloneDeep(AgreementHistoryModelMock);
      component.onValueChanged({ event: false  , value: false });
      expect(component.agreementsHistory[0].acceptance).not.toEqual('N/A');
    });

  });


});

Код компонента

 public onValueChanged(event) {
      if (IsNotNullOrUndefined(event.value)) {
            if (event.value) {
              this.agreementsHistory = this.agreementsHistoryData.filter(a => a.acceptance === 'N/A');
            } else {
              this.getNonCompletedAgreements();
            }
      }
    }