Angular Spectator：更改模拟的服务属性

如何解决Angular Spectator：更改模拟的服务属性

我正在使用观众和玩笑进行角度测试。我想在以下设置中更改模拟服务的属性：

describe('SearchComponent',() => {
  let spectator: spectator<SearchComponent>;

  const createComponent = createComponentFactory({
    component: SearchComponent,providers: [
      mockProvider(SearchService,{
        isActive$: of(false),// to be changed
      }),],shallow: true,});

  beforeEach(() => {
    spectator = createComponent();
  });

  it('should display bar if isActive(true)',() => {

  });

  it('should display foo if isActive(false)',() => {

  });

});

如何更改isActive $的值？