单元测试可通过延迟运算符观察 [英] Unit test Observable with delay operator

问题描述

我很难让我的单元测试与带有Observable的带延迟运算符一起工作.该应用程序基于Angular 2构建，并且测试在业力/茉莉花中运行.我已经尝试过async和fakeAsync帮助器方法，但是它们都不起作用.

I have a hard time getting my unit test to work together with an Observable with delay operator. The application is built on Angular 2 and the tests are running in karma/jasmine. I've tried the async and fakeAsync helper methods but none of them are working.

这是一个简化的代码块(无Angular 2)，解释了我的问题.

Here's a simplified code block (without Angular 2) explaining my issue.

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

推荐答案

下面是一个示例，该示例演示了如何在有人仍在寻找答案的情况下，使用Angular 2+中的延迟运算符对Observable进行单元测试:

Here is an example on how to unit test an Observable with a delay operator in Angular 2+, should anyone still be looking for the answer:

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();
  }));
});

这篇关于单元测试可通过延迟运算符观察的文章就介绍到这了，希望我们推荐的答案对大家有所帮助，也希望大家多多支持IT屋！