使用Karma + Mocha做单元测试(VUE)

Karma（[ˈkɑrmə] 卡玛）是一个测试运行器，它可以呼起浏览器，加载测试脚本，然后运行测试用例
Mocha（[ˈmoʊkə] 摩卡）是一个单元测试框架/库，它可以用来写测试用例
Sinon（西农）是一个 spy / stub / mock 库，用以辅助测试（使用后才能理解）

步骤

1. 安装工具

npm i -D karma karma-chrome-launcher karma-mocha karma-sinon-chai mocha sinon sinon-chai karma-chai karma-chai-spies

2. 创建 karma 配置

// 新建 karma.conf.js，内容如下
 module.exports = function (config) {
     config.set({

         // base path that will be used to resolve all patterns (eg. files, exclude)
         basePath: '',
            // frameworks to use
            // available frameworks: https://npmjs.org/browse/keyword/karma-adapter
            frameworks: ['mocha', 'sinon-chai'],
            client: {
                chai: {
                    includeStack: true
                }
            },


            // list of files / patterns to load in the browser
            files: [
                'dist/**/*.test.js',
                'dist/**/*.test.css'
            ],


            // list of files / patterns to exclude
            exclude: [],


            // preprocess matching files before serving them to the browser
            // available preprocessors: https://npmjs.org/browse/keyword/karma-preprocessor
            preprocessors: {},


            // test results reporter to use
            // possible values: 'dots', 'progress'
            // available reporters: https://npmjs.org/browse/keyword/karma-reporter
            reporters: ['progress'],


            // web server port
            port: 9876,


            // enable / disable colors in the output (reporters and logs)
            colors: true,


            // level of logging
            // possible values: config.LOG_DISABLE || config.LOG_ERROR || config.LOG_WARN || config.LOG_INFO || config.LOG_DEBUG
            logLevel: config.LOG_INFO,


            // enable / disable watching file and executing tests whenever any file changes
            autoWatch: true,


            // start these browsers
            // available browser launchers: https://npmjs.org/browse/keyword/karma-launcher
            // 当需要使用在Travis做持续集成的时候，需要将浏览器设置为ChromeHeadless,表示是没有不需要界面的chrome
            browsers: ['ChromeHeadless'],


            // Continuous Integration mode
            // if true, Karma captures browsers, runs the tests and exits
            singleRun: false,

            // Concurrency level
            // how many browser should be started simultaneous
            concurrency: Infinity
        })
    }

3. 创建 test/button.test.js 文件（测试用例）
   如：

const expect = chai.expect;
 import Vue from 'vue'
 import Button from '../src/button'

 Vue.config.productionTip = false
 Vue.config.devtools = false

 describe('Button', () => {
     it('存在.', () => {
         expect(Button).to.be.ok
     })
     it('可以设置icon.', () => {
         const Constructor = Vue.extend(Button)
         const vm = new Constructor({
         propsData: {
             icon: 'settings'
         }
         }).$mount()
         const useElement = vm.$el.querySelector('use')
         expect(useElement.getAttribute('xlink:href')).to.equal('#i-settings')
         vm.$destroy()
     })
     it('可以设置loading.', () => {
         const Constructor = Vue.extend(Button)
         const vm = new Constructor({
         propsData: {
             icon: 'settings',
             loading: true
         }
         }).$mount()
         const useElements = vm.$el.querySelectorAll('use')
         expect(useElements.length).to.equal(1)
         expect(useElements[0].getAttribute('xlink:href')).to.equal('#i-loading')
         vm.$destroy()
     })
     it('icon 默认的 order 是 1', () => {
         const div = document.createElement('div')
         document.body.appendChild(div)
         const Constructor = Vue.extend(Button)
         const vm = new Constructor({
         propsData: {
             icon: 'settings',
         }
         }).$mount(div)
         const icon = vm.$el.querySelector('svg')
         expect(getComputedStyle(icon).order).to.eq('1')
         vm.$el.remove()
         vm.$destroy()
     })
     it('设置 iconPosition 可以改变 order', () => {
         const div = document.createElement('div')
         document.body.appendChild(div)
         const Constructor = Vue.extend(Button)
         const vm = new Constructor({
         propsData: {
             icon: 'settings',
             iconPosition: 'right'
         }
         }).$mount(div)
         const icon = vm.$el.querySelector('svg')
         expect(getComputedStyle(icon).order).to.eq('2')
         vm.$el.remove()
         vm.$destroy()
     })
     it('点击 button 触发 click 事件', () => {
         const Constructor = Vue.extend(Button)
         const vm = new Constructor({
         propsData: {
             icon: 'settings',
         }
         }).$mount()

         const callback = sinon.fake();
         vm.$on('click', callback)
         vm.$el.click()
         expect(callback).to.have.been.called

     })
 })

4. 创建测试脚本

在 package.json 里面找到 scripts 并改写 scripts

 "scripts": {
     "dev-test": "parcel watch test/* --no-cache & karma start",
     "test": "parcel build test/* --no-minify && karma start --single-run"
 }

5. 运行测试用例

dev-test：
    这是持续运行，当新增组件和用例进行代码保存的时候就会执行

test：
    这是一次性运行