unit-testing - 运行使用 "Cannot use setInterval from within an async zone test"调用 setTimeout 错误的 Angular2 测试

Question

我正在升级我们的 Angular2 应用程序以使用 rc4，但我的单元测试开始出现错误:

Cannot use setInterval from within an async zone test

我的小部件从其 ngOnInit 方法请求数据，并在发出该请求时放置一个加载指示器。我的模拟服务在 1 毫秒后返回一些数据。

这是暴露问题的简化版本

import { inject, async, TestComponentBuilder, ComponentFixture} from '@angular/core/testing';
import {Http, Headers, RequestOptions, Response, HTTP_PROVIDERS} from '@angular/http';
import {provide, Component} from '@angular/core';

import {Observable} from "rxjs/Rx";

class MyService {
    constructor(private _http: Http) {}
    getData() {
        return this._http.get('/some/rule').map(resp => resp.text());
    }
}

@Component({
    template: `<div>
      <div class="loader" *ngIf="_isLoading">Loading</div>
      <div class="data" *ngIf="_data">{{_data}}</div>
    </div>`
})
class FakeComponent {
    private _isLoading: boolean = false;
    private _data: string = '';

    constructor(private _service: MyService) {}

    ngOnInit() {
        this._isLoading = true;
        this._service.getData().subscribe(data => {
            this._isLoading = false;
            this._data = data;
        });
    }
}

describe('FakeComponent', () => {
    var service = new MyService(null);
    var _fixture:ComponentFixture<FakeComponent>;

    beforeEach(async(inject([TestComponentBuilder], (tcb:TestComponentBuilder) => {
        return tcb
            .overrideProviders(FakeComponent, [
                HTTP_PROVIDERS,
                provide(MyService, {useValue: service}),
            ])
            .createAsync(FakeComponent)
            .then((fixture:ComponentFixture<FakeComponent>) => {
                _fixture = fixture;
            });
    })));

    it('Shows loading while fetching data', (cb) => {
        // Make the call to getData take one ms so we can verify its state while the request is pending
        // Error occurs here, when the widget is initialized and sends out an XHR
        spyOn(service, 'getData').and.returnValue(Observable.of('value').delay(1));
        _fixture.detectChanges();
        expect(_fixture.nativeElement.querySelector('.loader')).toBeTruthy();
        // Wait a few ms, should not be loading
        // This doesn't seem to be the problem
        setTimeout(() => {
            _fixture.detectChanges();
            expect(_fixture.nativeElement.querySelector('.loader')).toBeFalsy();
            cb();
        }, 10);
    });
});

这在 Angular2 rc1 中运行良好，但在 rc4 中抛出错误，有什么建议吗？

此外，如果您直接从测试本身使用 setTimeout，则不会出现错误

        fit('lets you run timeouts', async(() => {
            setTimeout(() => {
                expect(1).toBe(1);
            }, 10);
        }));

Answer 1

我发现出于某种原因，您不能在测试中使用通过 Observable.of(anything).delay() 创建的 promise 。

我的解决方案是自己实现该行，考虑到问题中发布的另一个示例确实有效，这几乎是有道理的。

// This is what we should be doing, but somehow, it isn't working.
// return Observable.of(result).delay(0));
function createDelayedObservable <T>(result:any, time:number = 0):Observable<T> {
    return new Observable<T>(observer => {
        setTimeout(() =>  observer.next(result), time);
    });
}

但是，我仍然不明白为什么以下不会失败，所以我不接受我自己的回答，希望对区域有深入了解的人可以告诉我发生了什么。

it('should be able to use delay in tests', (cb) => {
    var obs = Observable.of(1).delay(0);
    obs.subscribe(val => {
        expect(val).toBe(1);
        cb()
    });
});