取消订阅后，Jest测试用例将关闭ngdestroy上的对话框

Question

取消订阅后，我需要在ng destroy上编写开玩笑的测试用例。 但是测试没有通过给我错误关闭不是一种方法。

ts文件

ngOnDestroy() {
    this.subscriptions.forEach(subscription => subscription.unsubscribe());
    if (this.dialogRef) {
      this.dialogRef.close();
    }

规格文件

 //Mocking MatDialogRef from angular material
    const dialogReference = {
        afterOpen: () => Observable.of(),
        beforeClose: () => Observable.of(),
        close: () => Observable.of()
      };


      it('function should close the dialog on ngOnDestroy', () => {
          component.ngOnDestroy();
          fixture.detectChanges();
          //const dialogCloseSpy = spyOn(dialogReference, 'close').and.callThrough();
          expect(component['dialogReference'].close()).toHaveBeenCalled();
        });