带setTimeout的角度单元测试

我的组件如下所示,在Init中,我从服务获取初始数据,然后每15秒调用一次相同的函数来更新该数据:

networkGraph: NetworkGraphComponent;
hideSpinner: boolean = false;
ngAfterViewInit() {
      this.getTopology();
}

getTopology() {
      clearTimeout(this.timeoutHandler);
      this.topologyService.getTopology().subscribe((topology: any) => {

            ...do stuff...

            if (topology) {

                setTimeout(()=>{ // hack to fix ngIf 
                    this.hideSpinner = true;
                });
                this.networkGraph.topology = topology;
                this.timeoutHandle = setTimeout(function(){
                    this.getTopology();
                }, 15000);
            }

    });

我应该如何编写单元测试来测试这一点?它总是说我有计时器在排队。我读过这个 https://medium.com/@golbie/angular-testing-async-stuff-in-the-fakedasync-zone-vs-providing-custom-schedulers-27a7f83c7774 并尝试了其中的内容,但我猜我做得不对,因为我仍然得到了相同的结果。

 it('should create the component', fakeAsync(()=>{
    tick(20000)
    fixture.detectChanges();
    fixture.whenStable().then(()=>{
        expect(component).toBeTruthy();
    })

}));