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+# 测试
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+
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+我们主要想针对 Vuex 中的 mutaions 和 actions 进行单元测试。
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+
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+### 测试 Mutations
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+
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+Mutations 很容易被测试,因为它们仅仅是一些完全依赖参数的函数。这里有一个小技巧,如果你在 `store.js` 文件中定义了 mutations,并且使用 ES2015 模块功能默认输出了 Vuex.Store 的实例,那么你仍然可以给 mutation 取个变量名然后把它输出去:
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+
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+``` js
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+const state = { ... }
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+
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+// mutations 作为命名输出对象
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+export const mutations = { ... }
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+
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+export default new Vuex.Store({
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+ state,
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+ mutations
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+})
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+```
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+
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+下面是用 Mocha + Chai 测试一个 mutation 的例子(实际上你可以用任何你喜欢的测试框架):
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+
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+``` js
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+// mutations.js
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+export const mutations = {
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+ increment: state => state.count++
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+}
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+```
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+
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+``` js
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+// mutations.spec.js
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+import { expect } from 'chai'
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+import { mutations } from './store'
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+
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+// 解构 mutations
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+const { increment } = mutations
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+
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+describe('mutations', () => {
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+ it('INCREMENT', () => {
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+ // 模拟状态
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+ const state = { count: 0 }
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+ // 应用 mutation
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+ increment(state)
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+ // 断言结果
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+ expect(state.count).to.equal(1)
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+ })
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+})
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+```
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+
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+### 测试 Actions
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+
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+Actions 应对起来略微棘手,因为它们可能需要调用外部的 API。当测试 actions 的时候,我们需要增加一个 mocking 服务层 —— 例如,我们可以把 API 调用抽象成服务,然后在测试文件中用 mock 服务回应 API 调用。为了便于解决 mock 依赖,可以用 Webpack 和 [inject-loader](https://github.com/plasticine/inject-loader) 打包测试文件。
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+
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+下面是一个测试异步 action 的例子:
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+
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+``` js
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+// actions.js
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+import shop from '../api/shop'
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+
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+export const getAllProducts = ({ dispatch }) => {
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+ dispatch('REQUEST_PRODUCTS')
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+ shop.getProducts(products => {
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+ dispatch('RECEIVE_PRODUCTS', products)
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+ })
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+}
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+```
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+
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+``` js
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+// actions.spec.js
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+
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+// 使用 require 语法处理内联 loaders。
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+// inject-loader 返回一个允许我们注入 mock 依赖的模块工厂
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+import { expect } from 'chai'
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+const actionsInjector = require('inject!./actions')
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+
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+// 使用 mocks 创建模块
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+const actions = actionsInjector({
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+ '../api/shop': {
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+ getProducts (cb) {
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+ setTimeout(() => {
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+ cb([ /* mocked response */ ])
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+ }, 100)
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+ }
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+ }
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+})
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+
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+// 用指定的 mutaions 测试 action 的辅助函数
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+const testAction = (action, args, state, expectedMutations, done) => {
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+ let count = 0
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+
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+ // 模拟提交
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+ const commit = (type, payload) => {
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+ const mutation = expectedMutations[count]
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+ expect(mutation.type).to.equal(type)
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+ if (payload) {
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+ expect(mutation.payload).to.deep.equal(payload)
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+ }
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+ count++
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+ if (count >= expectedMutations.length) {
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+ done()
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+ }
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+ }
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+
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+ // 用模拟的 store 和参数调用 action
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+ action({ commit, state }, ...args)
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+
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+ // 检查是否没有 mutation 被 dispatch
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+ if (expectedMutations.length === 0) {
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+ expect(count).to.equal(0)
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+ done()
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+ }
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+}
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+
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+describe('actions', () => {
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+ it('getAllProducts', done => {
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+ testAction(actions.getAllProducts, [], {}, [
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+ { type: 'REQUEST_PRODUCTS' },
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+ { type: 'RECEIVE_PRODUCTS', payload: { /* mocked response */ } }
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+ ], done)
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+ })
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+})
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+```
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+
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+### 测试 Getters
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+
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+如果你的 getter 包含很复杂的计算过程,很有必要测试它们。Getter 的测试与 mutation 一样直截了当。
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+
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+测试一个 getter 的示例:
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+
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+``` js
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+// getters.js
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+export const getters = {
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+ filteredProducts (state, { filterCategory }) {
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+ return state.products.filter(product => {
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+ return product.category === filterCategory
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+ })
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+ }
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+}
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+```
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+
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+``` js
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+// getters.spec.js
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+import { expect } from 'chai'
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+import { getters } from './getters'
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+
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+describe('getters', () => {
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+ it('filteredProducts', () => {
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+ // 模拟状态
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+ const state = {
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+ products: [
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+ { id: 1, title: 'Apple', category: 'fruit' },
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+ { id: 2, title: 'Orange', category: 'fruit' },
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+ { id: 3, title: 'Carrot', category: 'vegetable' }
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+ ]
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+ }
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+ // 模拟 getter
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+ const filterCategory = 'fruit'
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+
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+ // 获取 getter 的结果
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+ const result = getters.filteredProducts(state, { filterCategory })
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+
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+ // 断言结果
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+ expect(result).to.deep.equal([
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+ { id: 1, title: 'Apple', category: 'fruit' },
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+ { id: 2, title: 'Orange', category: 'fruit' }
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+ ])
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+ })
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+})
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+```
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+
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+### 执行测试
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+
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+如果你的 mutations 和 actions 编写正确,经过合理地 mocking 处理之后这些测试应该不依赖任何浏览器 API,因此你可以直接用 Webpack 打包这些测试文件然后在 Node 中执行。换种方式,你也可以用 `mocha-loader` 或 `Karma` + `karma-webpack`在真实浏览器环境中进行测试。
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+
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+#### 在 Node 中执行测试
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+
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+创建以下 webpack 配置(配置好 [`.babelrc`](https://babeljs.io/docs/usage/babelrc/)):
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+
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+``` js
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+// webpack.config.js
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+module.exports = {
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+ entry: './test.js',
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+ output: {
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+ path: __dirname,
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+ filename: 'test-bundle.js'
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+ },
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+ module: {
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+ loaders: [
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+ {
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+ test: /\.js$/,
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+ loader: 'babel',
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+ exclude: /node_modules/
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+ }
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+ ]
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+ }
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+}
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+```
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+
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+然后:
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+
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+``` bash
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+webpack
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+mocha test-bundle.js
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+```
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+
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+#### 在浏览器中测试
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+
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+1. 安装 `mocha-loader`
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+2. 把上述 webpack 配置中的 `entry` 改成 `'mocha!babel!./test.js'`
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+3. 用以上配置启动 `webpack-dev-server`
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+4. 访问 `localhost:8080/webpack-dev-server/test-bundle`.
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+
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+#### 使用 Karma + karma-webpack 在浏览器中执行测试
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+
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+详见 [vue-loader documentation](http://vuejs.github.io/vue-loader/workflow/testing.html)。
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