使用 Karma + Mocha做单元测试

1. 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
2. Mocha（[ˈmoʊkə] 摩卡）是一个单元测试框架/库，它可以用来写测试用例
3. Sinon（西农）是一个 spy / stub / mock 库，用以辅助测试（使用后才能理解）
4. Chai js断言库，推荐expect写法

步骤

1. 安装各种工具
   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
            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

    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. 运行测试脚本

   1. 要么使用 npm run test 一次性运行

   2. 要么使用 npm run dev-test 进行 watch 运行（注意：Windows 用户运行 npm run dev-test 时会出现 BUG，解决办法是：
      将 dev-test 对应的命令 parcel watch test/* --no-cache & karma start 分别运行，运行方式如下
      新开一个 Git Bash 窗口运行 npx parcel watch test/* --no-cache
      再开一个 Git Bash 窗口运行 npx karma start）