单元测试使用延迟运算符观察

Question

我很难让我的单元测试与具有延迟操作符的Observable一起工作.该应用程序基于Angular 2构建,测试在karma/jasmine中运行.我已经尝试过async和fakeAsync帮助器方法,但它们都没有工作.

这是一个简化的代码块(没有Angular 2)解释我的问题.

let mouseDownStream = Rx.Observable.fromEvent(document.body, 'mousedown');
let haveBeenCalled = false;
mouseDownStream.delay(200).subscribe(() => haveBeenCalled = true);

describe('mouse down event', () => {
  it('it should emit an event stream after 200ms', (done) => {
    document.body.dispatchEvent(new MouseEvent('mousedown'))
    expect(haveBeenCalled).toBeFalsy();

    // Don't want this setTimeout should use Angular's tick(200) method instead but it's not working.
    setTimeout(() => {
      expect(haveBeenCalled).toBeTruthy();
      done();
    }, 200)
  });
});

JSBin

Answer 1

下面是一个关于如何在 Angular 2+ 中使用延迟运算符对 Observable 进行单元测试的示例，如果有人仍在寻找答案的话：

import { fakeAsync, tick } from "@angular/core/testing";

import { fromEvent } from "rxjs";
import { delay } from "rxjs/operators";

describe("mouse down event", () => {
  it("should emit an event stream after 200ms", fakeAsync(() => {
    let mouseDownStream = fromEvent(document.body, "mousedown");
    let haveBeenCalled = false;

    const subscription = mouseDownStream.pipe(delay(200)).subscribe(() => (haveBeenCalled = true));
    document.body.dispatchEvent(new MouseEvent("mousedown"));

    expect(haveBeenCalled).toBeFalsy();

    tick(200);

    expect(haveBeenCalled).toBeTruthy();

    subscription.unsubscribe();
  }));
});