如何以角度编写viewchild elementRef的单元测试用例

Question

在打字稿文件中

  @ViewChild(sampleFileComponent) datafiles: sampleFileComponent;
  @ViewChild(sampleFileComponent, { read: ElementRef })
  sampleFileElementRef: ElementRef;

private sample(event: any): void {
  const  nodeId= event.data.entry.id;// nodeId="123"
  this.datafiles.test=nodeId;
  this.sampleFileElementRef.nativeElement.querySelector('label').click();
  }

如何为此功能编写单元测试