养成良好的编码习惯，一个合格的程序员需要掌握一些编写单元测试的能力。单元测试也可以整体上提升我们的代码质量，这里介绍下 VUE 组件的单元测试。
如果想直接通过 Demo 学习，可以跳过下面的内容，点击这里下载示例
技术栈
定义配置文件
karma.conf.js 文件用于 karma 的配置，使用 node_modules/.bin/karma init 命令创建该文件，我们定义如下配置：
// Karma configuration
const webpackConfig = require('./config/webpack.test.config.js')
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' ],
// list of files / patterns to load in the browser
files: [
'test/**/*.spec.js'
],
// preprocess matching files before serving them to the browser
// available preprocessors: https://npmjs.org/browse/keyword/karma-preprocessor
preprocessors: {
'test/**/*.spec.js': [ 'webpack', 'sourcemap' ]
},
// webpack config
webpack: webpackConfig,
webpackMiddleware: {
stats: 'errors-only'
},
// 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: [ 'Chrome' ],
// 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
})
}
编写测试用例
详细的关于 @vue/test-utils 用法，查看 https://vue-test-utils.vuejs.org/zh/
import { expect } from 'chai'
import { shallowMount } from '@vue/test-utils'
import Header from '../src/components/Header'
describe('Header', () => {
const wrapper = shallowMount(Header)
const header = wrapper.find('header')
const h1 = wrapper.find('h1')
it('有 header 标签', () => {
expect(header.exists()).to.be.true
})
it('有 h1 标签', () => {
expect(h1.exists()).to.be.true
})
it('h1 的文案为“VUE 单页模版”', () => {
expect(h1.text()).to.equal('VUE 单页模版')
})
it('h1 标签在 header 标签中', () => {
expect(header.contains('h1')).to.be.true
})
})
这里我引用 vue-single-page 的 Header 组件测试用例
运行结果
i ｢wdm｣: Compiled successfully.
15 01 2020 18:28:13.799:INFO [karma-server]: Karma v4.4.1 server started at http://0.0.0.0:9876/
15 01 2020 18:28:13.813:INFO [launcher]: Launching browsers Chrome with concurrency unlimited
15 01 2020 18:28:13.820:INFO [launcher]: Starting browser Chrome
15 01 2020 18:28:17.075:INFO [Chrome 79.0.3945 (Windows 10.0.0)]: Connected on socket PUKPz4iBuFzeVNSsAAAA with id 91716917
TOTAL: 4 SUCCESS
可以看到我们的单元测试已经通过了
测试覆盖率报告
测试完成后，我们需要查看测试覆盖率报告。这需要在 webpack.test.config.js 和 karma.conf.js 中做一些配置修改
webpack.test.config.js
const merge = require('webpack-merge')
const path = require('path')
const webpackCommonConfig = require('./webpack.common.config')
const testConfig = {
devtool: 'inline-source-map',
mode: 'none',
module: {
rules: [
{
test: /\.spec.js$/i,
enforce: 'pre',
use: [
{
loader: 'istanbul-instrumenter-loader',
options: {
esModules: true
}
}
]
}
]
}
}
module.exports = merge(webpackCommonConfig, testConfig)
添加一个优先执行的编译 .spec.js 文件的 rules，loader 使用 istanbul-instrumenter-loader 并开启 esModules 模式
karma.conf.js
module.exports = function(config) {
config.set({
// ...
coverageIstanbulReporter: {
reports: [ 'html', 'text' ],
fixWebpackSourcePaths: true
},
reporters: [ 'coverage-istanbul' ]
//...
})
}
运行结果
再次执行单元测试，我们会看到测试覆盖率的相关信息
----------------|----------|----------|----------|----------|-------------------| File | % Stmts | % Branch | % Funcs | % Lines | Uncovered Line #s | ----------------|----------|----------|----------|----------|-------------------| All files | 100 | 100 | 100 | 100 | | Header.spec.js | 100 | 100 | 100 | 100 | | ----------------|----------|----------|----------|----------|-------------------|
也可以通过生成到 coverage 目录下的网页文件，在浏览器中查看
参考资料
https://vue-test-utils.vuejs.org/zh/
https://github.com/mattlewis92/karma-coverage-istanbul-reporter
以上就是本文的全部内容，希望对大家的学习有所帮助，也希望大家多多支持脚本之家。
