Angularjs 当我向构造函数添加服务时，Fixture.detectChanges的行为非常奇怪

我有一个父组件：

 @Component({
selector: 'parent-component',
directives: [I18nDirective, child-component],
template: require('./parent.component.html'),
styles: [require('./parent.component.scss')],
})
export class ParentComponent {
}

@Component({
selector: 'child-component',
template: require('./child-component.component.html'),
styles: [require('./child-component.component.scss')]
})
export class ChildComponent {

constructor(private _eventAggregator: EventAggregatorService, private _zone: NgZone) {}

然后我有子组件：

 @Component({
selector: 'parent-component',
directives: [I18nDirective, child-component],
template: require('./parent.component.html'),
styles: [require('./parent.component.scss')],
})
export class ParentComponent {
}

@Component({
selector: 'child-component',
template: require('./child-component.component.html'),
styles: [require('./child-component.component.scss')]
})
export class ChildComponent {

constructor(private _eventAggregator: EventAggregatorService, private _zone: NgZone) {}

在父组件的html中，我使用：子组件

问题在于子组件的规格测试。在以下情况下通过测试：

describe('Center On Me Button', () => {

let fixture;
let nativeElement;
let componentInstance;

beforeEachProviders(() => [
    ChildComponent,
    EventAggregatorService,
    GeoLocationService,
    provide(GoogleMapsAPIWrapper, {useClass: StabGoogleMapsApiWrapper}),
    provide(MapController, {useClass: StabMapControllerService}),
    provide(MapEventsService, {useClass: StabMapEventsService})
]);

beforeEach(injectAsync([TestComponentBuilder, GoogleMapsAPIWrapper, GeoLocationService, MapController, EventAggregatorService
    ], (tcb: TestComponentBuilder ) => {

    return tcb
        .createAsync(ChildComponent).then((componentFixture: ComponentFixture<ChildComponent>) => {

            ({nativeElement, componentInstance} = componentFixture);
            fixture = componentFixture;
            componentFixture.detectChanges();
        });

 it('should enable Geolocation button when it is clicked', done => {
    componentInstance.isGeoLocationButtonEnabled = false;
    nativeElement.querySelector('.toggle.fa.fa-crosshairs').click();
    expect(componentInstance.isGeoLocationButtonEnabled).toBe(true);
    done();
});
}));

我所做的只是将：私有someService:someService添加到子组件的构造函数中。因此我现在：

export class ChildComponent {

constructor(private _eventAggregator: EventAggregatorService, private _zone: NgZone, private _someService: SomeService) {}

我添加的这项服务被添加到angular应用程序顶层的提供者列表中。当然，我将它添加到测试本身的提供者列表中

---

当我这样做时，测试开始失败，与我写的前一条消息。这到底是为什么？我真的不明白这种行为，而且网络上的资源有限。还没有文档。

可能不是这样：当我添加private\u geoLocationService:geoLocationService时，我会得到相同的行为，并且在每个提供程序之前插入geolocation服务。