angular - 为什么异步 Angular 单元测试找不到 DOM 元素？

Question

我有一个失败的异步 Angular 组件 DOM 测试，但它的同步等效失败，我不明白为什么。

这是 Jasmine 测试:

describe('Availability Component', () => {

    let fixture: ComponentFixture<AvailabilityComponent>;

    const absenceService = jasmine.createSpyObj('AbsenceService', ['findAbsences']);
    absenceService.findAbsences.and.returnValue(of([{}]));

    beforeEach(async(() => {
        TestBed.configureTestingModule({
            declarations: [AvailabilityComponent],
            imports: [CalendarModule.forRoot()],
            providers: [{provide: AbsenceService, useValue: absenceService}]
        }).compileComponents();
    }));

    beforeEach(() => {
        fixture = TestBed.createComponent(AvailabilityComponent);
    });

    const printAbsenceReasons = function () {
        console.log(fixture.debugElement.queryAll(By.css('.calendarAbsence'))
        .map(e => e.nativeElement.textContent)
        .join(','));
    };

    it('should synchronously find absences in calendar view', () => {
        fixture.detectChanges();

        console.log('synchronous test');
        printAbsenceReasons();
    });

    it('should  asynchronously find absences in calendar view', fakeAsync(() => {
        fixture.detectChanges();
        tick();
        fixture.detectChanges();
        tick();

        console.log('asynchronous test');
        printAbsenceReasons();
    }));
});

在同步情况下创建正确的输出但在异步情况下不正确:

LOG: 'processing absences'
HeadlessChrome 0.0.0 (Mac OS X 10.13.4): Executed 0 of 51 SUCCESS (0 secs / 0 secs)
LOG: 'synchronous test'
HeadlessChrome 0.0.0 (Mac OS X 10.13.4): Executed 0 of 51 SUCCESS (0 secs / 0 secs)
LOG: 'A,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,'
HeadlessChrome 0.0.0 (Mac OS X 10.13.4): Executed 0 of 51 SUCCESS (0 secs / 0 secs)
ERROR: 'Spec 'Availability Component should synchronously find absences in calendar view' has no expectations.'
HeadlessChrome 0.0.0 (Mac OS X 10.13.4): Executed 0 of 51 SUCCESS (0 secs / 0 secs)
LOG: 'processing absences'
HeadlessChrome 0.0.0 (Mac OS X 10.13.4): Executed 1 of 51 SUCCESS (0 secs / 0 secs)
LOG: 'asynchronous test'
HeadlessChrome 0.0.0 (Mac OS X 10.13.4): Executed 1 of 51 SUCCESS (0 secs / 0 secs)
LOG: ''
HeadlessChrome 0.0.0 (Mac OS X 10.13.4): Executed 1 of 51 SUCCESS (0 secs / 0 secs)
ERROR: 'Spec 'Availability Component should  asynchronously find absences in calendar view' has no expectations.'

我不确定这是否与 angular-calendar 有关我正在使用的组件，或者它是否是我的测试代码的一个更基本的问题。

供引用的是我的组件、模板和服务代码:

@Component({
    selector: 'app-availability',
    templateUrl: './availability.component.html',
    styleUrls: ['availability.component.scss']
})
export class AvailabilityComponent implements OnInit {
    viewDate: Date = new Date();
    absenceEvents: CalendarEvent[] = [];

    constructor(private absenceService: AbsenceService) {
    }

    ngOnInit() {
        this.getAbsences();
    }

    getAbsences() {
        this.absenceService.findAbsences()
        .subscribe(ignored => {
            console.log('processing absences');
            this.absenceEvents = [{
                start: new Date(2018, 3, 29), title: 'A'
            }];
        });
    }

    getAbsence(events: CalendarEvent[]) {
        return events[0] ? events[0].title : '';
    }
}

模板代码:

<div>
    <div>
        <mwl-calendar-month-view
            [viewDate]="viewDate"
            [events]="absenceEvents"
            [cellTemplate]="availabilityCellTemplate">
        </mwl-calendar-month-view>
    </div>
    <ng-template #availabilityCellTemplate let-day="day">
        <div class="calendarAbsence">{{ getAbsence(day.events) }}</div>
    </ng-template>
</div>  

服务代码:

@Injectable()
export class AbsenceService {

    private url = environment.APP_SHIFT_SERVICE_BASE_URL + '/api/absences';

    constructor(private http: HttpClient) {
    }

    findAbsences(): Observable<Absence[]> {
        console.error('Actual findAbsences() called');
        return this.http.get<Absence[]>(this.url);
    }
}

Answer 1

不幸的是，这似乎特别与 fakeAsync 区域有关，而不是特别与异步测试有关。

我已经设法获得一个工作异步测试来使用 async 而不是 fakeAsync:

it('should asynchronously find absences in calendar view', async(() => {
        fixture.detectChanges();

        fixture.whenStable().then(() => {
            console.log('asynchronous test');
            printAbsenceReasons(fixture);

            expect(getAbsenceElements(fixture).length).toEqual(35);
        });
    });
}));

我已经调试了失败的 fakeAsync 和成功的同步测试。他们都在库“calendar-utils”中调用一个名为 getMonthView 的方法，作者与“angular-calendar”相同: https://github.com/mattlewis92/calendar-utils/blob/master/src/calendar-utils.ts

在此method Date 参数和其他 Date 计算本身似乎都出错了。

目前我只能假设它与这个 known issue in zone.js 有关.我在使用 Angular 5.2，但我认为它仍然相关。无论如何，我确信我的测试代码基本上是正确的，但问题出在其他地方。