我正在做一些單元測試。所以我有這個功能：selectCluster(event: MouseEvent, feature: any) {    event.stopPropagation();     this.selectedCluster = {geometry: feature.geometry, properties: feature.properties};  }和模板： <mgl-popup *ngIf="selectedCluster" [feature]="selectedCluster">          </mgl-popup>我有這樣的測試：  fit('Should set selectedCluster when clicked', async(() => {        spyOn(component, 'selectCluster').and.callThrough();    fixture.detectChanges();    fixture.debugElement.query(By.css('.marker-cluster')).nativeElement.click();    tick();    fixture.whenStable().then(() => {      expect(component.selectCluster).toHaveBeenCalled();    });  }));但我仍然收到此錯誤：Cannot read property 'nativeElement' of null那么我必須改變什么？謝謝這也使用了以下函數： <ng-template mglClusterPoint let-feature>        <div class="marker-cluster" (click)="selectCluster($event, feature)">          <fa-icon [icon]="faVideo" [styles]="{'stroke': 'black', 'color': 'black'}" size="lg" class="pr-2"></fa-icon>          <fa-icon [icon]="faWifi" [styles]="{'stroke': 'black', 'color': 'black'}" size="lg" class="pr-2"></fa-icon>        </div>      </ng-template>