10|mock timers的使用

一、mock timers的使用

// timer.js
export const timer = (callback) => {
    setTimeout(() => {
        callback()
    },3000)
}

// timer.test.js
import { timer } from './timer'
jest.useFakeTimers();
test('timer 测试', () => {
    const fn = jest.fn();
    timer(fn);
    jest.runAllTimers();
    expect(fn).toHaveBeenCalledTimes(1);
})

二、runOnlyPendingTimers 运行只处于队列中任务

//timer
export const timer = (callback) => {
    setTimeout(() => {
        callback()
        setTimeout(() => {
            callback()
        })
    },3000)
}

//timer.test.js
import { timer } from './timer'
jest.useFakeTimers();
test('timer 测试', () => {
    const fn = jest.fn();
    timer(fn);
    jest.runOnlyPendingTimers();
    expect(fn).toHaveBeenCalledTimes(1);
})

三、advanceTimersByTime 时间快进

// timer.js
export const timer = (callback) => {
    setTimeout(() => {
        callback()
        setTimeout(() => {
            callback()
        },3000)
    },3000)
}

// timer.test.js
import { timer } from './timer'
jest.useFakeTimers();
test('timer 测试', () => {
    const fn = jest.fn();
    timer(fn);
    jest.advanceTimersByTime(3000);
    expect(fn).toHaveBeenCalledTimes(1);
})

四、排除各测试之间的干扰

import { timer } from './timer'
beforeEach(() => {
    jest.useFakeTimers()
})
test('timer 测试', () => {
    const fn = jest.fn();
    timer(fn);
    jest.advanceTimersByTime(3000);
    expect(fn).toHaveBeenCalledTimes(1);
    jest.advanceTimersByTime(3000);
    expect(fn).toHaveBeenCalledTimes(2);
})

test('timer1 测试', () => {
    const fn = jest.fn();
    timer(fn);
    jest.advanceTimersByTime(3000);
    expect(fn).toHaveBeenCalledTimes(1);
    jest.advanceTimersByTime(3000);
    expect(fn).toHaveBeenCalledTimes(2);
})