javascript - 模拟 delay() RxJS 与 Jest

Question

例如，是否有简单的方法在一个带有假时间的可观察对象中模拟 RxJS 的 delay() 方法？

我有这个方法:

register(user) {
  return this._checkLog(user).delay(500).flatMap( ... )
}

当我删除 delay() 方法时，我对 _register() 的测试全部成功。

Answer 1

RxJS v6

对于这样的 RxJS v6 代码:

代码.js

import { of } from 'rxjs';
import { delay } from 'rxjs/operators';

export const example = of('hello').pipe(
  delay(1000)
);

---

...你可以使用sinon fake timers像这样:

import * as sinon from 'sinon';
import { example } from './code';

describe('delay', () => {
  let clock;
  beforeEach(() => { clock = sinon.useFakeTimers(); });
  afterEach(() => { clock.restore(); });

  it('should delay one second', () => {
    const spy = jest.fn();
    example.subscribe(spy);

    expect(spy).not.toHaveBeenCalled();  // Success!
    clock.tick(1000);
    expect(spy).toHaveBeenCalledWith('hello');  // Success!
  });
});

(请注意，在撰写本文时 Jest timer mocks 不起作用，不确定原因)

---

...或者你可以模拟 delay 不做这样的事情:

import { delay } from 'rxjs/operators';
import { example } from './code';

jest.mock('rxjs/operators', () => {
  const operators = jest.requireActual('rxjs/operators');
  operators.delay = jest.fn(() => (s) => s);  // <= mock delay
  return operators;
});

describe('delay', () => {
  it('should delay one second', () => {
    const spy = jest.fn();
    example.subscribe(spy);

    expect(delay).toHaveBeenCalledWith(1000);  // Success!
    expect(spy).toHaveBeenCalledWith('hello');  // Success!
  });
});

---

RxJS v5

对于这样的 RxJS v5 代码:

代码.js

import { Observable } from 'rxjs/Observable';
import 'rxjs/add/observable/of';
import 'rxjs/add/operator/delay';

export const example = Observable.of('hello').delay(1000);

...你可以模拟 delay 不做这样的事情:

import { Observable } from 'rxjs/Observable';
import { example } from './code';

jest.mock('rxjs/add/operator/delay', () => {
  const Observable = require('rxjs/Observable').Observable;
  Observable.prototype.delay = jest.fn(function () { return this; });  // <= mock delay
});

describe('delay', () => {
  it('should delay one second', () => {
    const spy = jest.fn();
    example.subscribe(spy);

    expect(Observable.prototype.delay).toHaveBeenCalledWith(1000);  // Success!
    expect(spy).toHaveBeenCalledWith('hello');  // Success!
  });
});