如何在angular 2中编写测试，以检查子组件中是否设置了输入变量？

My app.component有一个名为“environment”的属性，该属性是使用http服务设置的，下面是组件

app.component.ts

//import ..

@Component({
  selector: 'my-app',
  template: require('./app.component.html')
})

export class AppComponent {
  myEnvironment: String;
  workbenchBaseUrl : String = 'workbenchBaseUrl';

  constructor(private _propertyService : PropertyService){
  }

  ngOnInit(): void {
    this._propertyService.getValue(this.workbenchBaseUrl)
        .subscribe(environment => this.myEnvironment = environment,
            error => this.errorMessage = <any>error);
  }


}

现在，我正在尝试为workdisplay.component编写单元测试，以确保它设置了环境变量，但我不确定如何测试它，因为它仅在父组件中的回调之后设置，并且一开始是未定义的。 这是我在规范中写的

工作流-display.spec

//import..

describe('WorkflowDisplayComponent (inline template)', () => {

    let comp:    WorkflowDisplayComponent;
    let fixture: ComponentFixture<WorkflowDisplayComponent>;


    beforeEach(async(() => {
        TestBed.configureTestingModule({
            declarations: [ WorkflowDisplayComponent ], // declare the test component
            providers: [WorkflowService,
                        MockBackend,
                        BaseRequestOptions,
                        {
                        provide: Http,
                        deps: [MockBackend, BaseRequestOptions],
                        useFactory:
                            (backend: XHRBackend, defaultOptions: BaseRequestOptions) => {
                                return new Http(backend, defaultOptions);
                            }
                        }
            ]
        }).compileComponents();

        fixture = TestBed.createComponent(WorkflowDisplayComponent);

        comp = fixture.componentInstance; // BannerComponent test instance


    }));

    it('should have right URL', () => {
        fixture.detectChanges();
        expect((comp.environment + comp.workbenchTaskPage)).toEqual('http://dev.grc.coreworkbench.int.westgroup.com/grcworkbench/app/grcnewsalerts/wsIndex');
    });
});

---

现在我看到子组件环境变量还没有定义，我不知道如何解决这个问题。应该测试应用程序组件，以确保其“myEnvironment”变量已设置或其他内容

你得到答案了吗？

    //import ..

    @Component({
        selector: 'workflow-display',
        template: require('./workflow-display.component.html')
    })
    export class WorkflowDisplayComponent implements OnInit {

        //some other variables hidden...
        workbenchTaskPage: string = 'wsIndex'; 
        @Input()
        environment: String;

        constructor(private _workflowService: WorkflowService) {

        }

        openTask(event: any, task: any) {
          window.open(this.environment + this.workbenchTaskPage + "?taskId=" + task.taskId + "&activitiWorkflow=true");
        }

 }

//import..

describe('WorkflowDisplayComponent (inline template)', () => {

    let comp:    WorkflowDisplayComponent;
    let fixture: ComponentFixture<WorkflowDisplayComponent>;


    beforeEach(async(() => {
        TestBed.configureTestingModule({
            declarations: [ WorkflowDisplayComponent ], // declare the test component
            providers: [WorkflowService,
                        MockBackend,
                        BaseRequestOptions,
                        {
                        provide: Http,
                        deps: [MockBackend, BaseRequestOptions],
                        useFactory:
                            (backend: XHRBackend, defaultOptions: BaseRequestOptions) => {
                                return new Http(backend, defaultOptions);
                            }
                        }
            ]
        }).compileComponents();

        fixture = TestBed.createComponent(WorkflowDisplayComponent);

        comp = fixture.componentInstance; // BannerComponent test instance


    }));

    it('should have right URL', () => {
        fixture.detectChanges();
        expect((comp.environment + comp.workbenchTaskPage)).toEqual('http://dev.grc.coreworkbench.int.westgroup.com/grcworkbench/app/grcnewsalerts/wsIndex');
    });
});

should have right URL FAILED
        Expected 'undefinedwsIndex' to equal 'http://dev.grc.coreworkbench.int.westgroup.com/grcworkbench/app/grcnewsalerts/wsIndex'.