React+Redux单元测试一小时入门

摘要：可以监控文件变化自动执行单元测试，可以缓存测试结果，可以显示测试过程中的变量测试框架。执行单元测试三测试在的理念中，组件应该分为视觉组件和高阶组件，与逻辑分离，更利于测试。

karma：测试过程管理工具。可以监控文件变化自动执行单元测试，可以缓存测试结果，可以console.log显示测试过程中的变量

mocha：测试框架。提供describe，it，beforeEach等函数管理你的 testcase，后面示例中会看到

chai：BDD（行为驱动开发）和TDD（测试驱动开发）双测试风格的断言库

enzyme：React测试工具，可以类似 jquery 风格的 api 操作react 节点

sinon: 提供 fake 数据， 替换函数调用等功能

工具安装就是 npm install，这里就不再详述，主要的配置项目在karma.conf.js中，可以参考这个模板项目 react-redux-starter-kit 。如果项目中用到全局变量，比如jquery, momentjs等，需要在测试环境中全局引入，否则报错，例如，在karma.conf中引入全局变量jQuery:

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{
    files: [
    "./node_modules/jquery/jquery.min.js",
    {
      pattern: `./tests/test-bundler.js`,
      watched: false,
      served: true,
      included: true
    }
  ]
}

在test-bundler.js中设置全局的变量，包括chai, sinon等：

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/* tests/test-bundler.js */
import "babel-polyfill"
import sinon from "sinon"
import chai from "chai"
import sinonChai from "sinon-chai"
import chaiAsPromised from "chai-as-promised"
import chaiEnzyme from "chai-enzyme"
chai.use(sinonChai)
chai.use(chaiAsPromised)
chai.use(chaiEnzyme())
global.chai = chai
global.sinon = sinon
global.expect = chai.expect
global.should = chai.should()
...

先热身看看简单的函数如何单元测试：

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/* helpers/validator.js */
export function checkUsername (name) {
  if (name.length === 0 || name.length > 15) {
    return "用户名必须为1-15个字"
  }
  return ""
}

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/* tests/helpers/validator.spec.js */
import * as Validators from "helpers/validator"
describe("helpers/validator", () => {
    describe("Function: checkUsername", () => {
        it("Should not return error while input foobar.", () => {
            expect(Validators.checkUsername("foobar")).to.be.empty
        })
        it("Should return error while empty.", () => {
            expect(Validators.checkUsername("")).to.equal("用户名必须为1-15个字")
        })
        it("Should return error while more then 15 words.", () => {
            expect(Validators.checkUsername("abcdefghijklmnop")).to.equal("用户名必须为1-15个字")
            expect(Validators.checkUsername("一二三四五六七八九十一二三四五六")).to.equal("用户名必须为1-15个字")
        })
    })
})

describe可以多次嵌套使用，更清晰的描述测试功能的结构。执行单元测试:
babel-node ./node_modules/karma/bin/karma start build/karma.conf

在 redux 的理念中，react 组件应该分为视觉组件 component 和 高阶组件 container，UI与逻辑分离，更利于测试。redux 的 example 里，这两种组件一般都分开文件去存放。本人认为，如果视觉组件需要多次复用，应该与container分开来写，但如果基本不复用，或者可以复用的组件已经专门组件化了(下面例子就是)，那就没必要分开写，可以写在一个文件里更方便管理，然后通过 export 和 export default 分别输出

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/* componets/Register.js  */
import React, { Component, PropTypes } from "react"
import { connect } from "react-redux"
import {
  FormGroup,
  FormControl,
  FormLabel,
  FormError,
  FormTip,
  Button,
  TextInput
} from "componentPath/basic/form"
export class Register extends Component {
  render () {
    const { register, onChangeUsername, onSubmit } = this.props
    
      
        用户名
        
          
          请输入用户名
          {register.usernameError}
        
      
      
        提交
      
    
  }
}
Register.propTypes = {
  register: PropTypes.object.isRequired,
  onChangeUsername: PropTypes.func.isRequired,
  onSubmit: PropTypes.func.isRequired
}
const mapStateToProps = (state) => {
  return {
    register: state.register
  }
}
const mapDispatchToProps = (dispatch) => {
  return {
    onChangeUsername: name => {
      ...
    },
    onSubmit: () => {
      ...
    }
  }
}
export default connect(mapStateToProps, mapDispatchToProps)(Register)

测试 componet，这里用到 enzyme 和 sinon：

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import React from "react"
import { bindActionCreators } from "redux"
import { Register } from "components/Register"
import { shallow } from "enzyme"
import {
  FormGroup,
  FormControl,
  FormLabel,
  FormError,
  FormTip,
  Dropdown,
  Button,
  TextInput
} from "componentPath/basic/form"
describe("rdappmsg/trade_edit/componets/Plan", () => {
  let _props, _spies, _wrapper
  let register = {
    username: "",
    usernameError: ""
  }
  beforeEach(() => {
    _spies = {}
    _props = {
      register,
      ...bindActionCreators({
        onChangeUsername: (_spies.onChangeUsername = sinon.spy()),
        onSubmit: (_spies.onSubmit = sinon.spy())
      }, _spies.dispatch = sinon.spy())
    }
    _wrapper = shallow()
  })
  it("Should render as a 
.", () => {
    expect(_wrapper.is("div")).to.equal(true)
  })
  it("Should has two children.", () => {
    expect(_wrapper.children()).to.have.length(2);
  })
  it("Each element of form should be .", () => {
      _wrapper.children().forEach(function (node) {
        expect(node.is(FormGroup)).to.equal(true);
      })
  })
  it("Should render username properly.", () => {
    expect(_wrapper.find(TextInput).prop("value")).to.be.empty
    _wrapper.setProps({register: {...register, username: "foobar" }})
    expect(_wrapper.find(TextInput).prop("value")).to.equal("foobar")
  })
  it("Should call onChangeUsername.", () => {
    _spies.onChangeUsername.should.have.not.been.called
    _wrapper.find(TextInput).prop("onChange")("hello")
    _spies.dispatch.should.have.been.called
    
  })
})

beforeEach函数在每个测试用例启动前做一些初始化工作

enzyme shallow 的用法跟 jquery 的dom操作类似，可以通过选择器过滤出想要的节点，可以接受 css 选择器或者react class，如：find(".someClass")， find(TextInput)

这里用到了 sinon 的spies, 可以观察到函数的调用情况。他还提供stub, mock功能，了解更多请 google

先来看一个普通的 action：

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/* actions/register.js */
import * as Validator from "helpers/validator"
export const CHANGE_USERNAME_ERROR = "CHANGE_USERNAME_ERROR"
export function checkUsername (name) {
  return {
    type: CHANGE_USERNAME_ERROR,
    error: Validator.checkUsername(name)
  }
}

普通的 action 就是一个简单的函数，返回一个 object，测试起来跟前面的简单函数例子一样:

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/* tests/actions/register.js */
import * as Actions from "actions/register"
describe("actions/register", () => {
  describe("Action: checkUsername", () => {
    it("Should export a constant CHANGE_USERNAME_ERROR.", () => {
      expect(Actions.CHANGE_USERNAME_ERROR).to.equal("CHANGE_USERNAME_ERROR")
    })
    it("Should be exported as a function.", () => {
      expect(Actions.checkUsername).to.be.a("function")
    })
    
    it("Should be return an action.", () => {
      const action = Actions.checkUsername("foobar")
      expect(action).to.have.property("type", Actions.CHANGE_USERNAME_ERROR)
    })
    
    it("Should be return an action with error while input empty name.", () => {
      const action = Actions.checkUsername("")
      expect(action).to.have.property("error").to.not.be.empty
    })   
  })
   
})

再来看一下异步 action, 这里功能是改变 username 的同时发起检查:

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export const CHANGE_USERNAME = "CHANGE_USERNAME"
export function changeUsername (name) {
  return (dispatch) => {
    dispatch({
      type: CHANGE_USERNAME,
      name
    })
    dispatch(checkUsername(name))
  }
}

测试代码：

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/* tests/actions/register.js */
import * as Actions from "actions/register"
describe("actions/register", () => {
  let actions
  let dispatchSpy
  let getStateSpy
  beforeEach(function() {
    actions = []
    dispatchSpy = sinon.spy(action => {
      actions.push(action)
    })
  })
  describe("Action: changeUsername", () => {
    it("Should export a constant CHANGE_USERNAME.", () => {
      expect(Actions.CHANGE_USERNAME).to.equal("CHANGE_USERNAME")
    })
    it("Should be exported as a function.", () => {
      expect(Actions.changeUsername).to.be.a("function")
    })
    
    it("Should return a function (is a thunk).", () => {
      expect(Actions.changeUsername()).to.be.a("function")
    })
    
    it("Should be return an action.", () => {
      const action = Actions.checkUsername("foobar")
      expect(action).to.have.property("type", Actions.CHANGE_USERNAME_ERROR)
    })
    
    it("Should call dispatch CHANGE_USERNAME and CHANGE_USERNAME_ERROR.", () => {
      Actions.changeUsername("hello")(dispatchSpy)
      dispatchSpy.should.have.been.calledTwice
      expect(actions[0]).to.have.property("type", Actions.CHANGE_USERNAME)
      expect(actions[0]).to.have.property("name", "hello")
      expect(actions[1]).to.have.property("type", Actions.CHANGE_USERNAME_ERROR)
      expect(actions[1]).to.have.property("error", "")
    }) 
  })
})

假如现在产品需求变更，要求实时在后台检查 username 的合法性, 就需要用到 ajax 了, 这里假设使用 Jquery 来实现 ajax 请求:

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/* actions/register.js */
export const CHANGE_USERNAME_ERROR = "CHANGE_USERNAME_ERROR"
export function checkUsername (name) {
  return (dispatch) => {
    $.get("/check", {username: name}, (msg) => {
      dispatch({
        type: CHANGE_USERNAME_ERROR,
        error: msg
      })
    })
  }
}

要测试 ajax 请求，可以用 sinon 的 fake XMLHttpRequest, 不用为了测试改动 action 任何代码:

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/* tests/actions/register.js */
import * as Actions from "actions/register"
describe("actions/register", () => {
  let actions
  let dispatchSpy
  let getStateSpy
  let xhr
  let requests
  beforeEach(function() {
    actions = []
    dispatchSpy = sinon.spy(action => {
      actions.push(action)
    })
    
    xhr = sinon.useFakeXMLHttpRequest()
    requests = []
    xhr.onCreate = function(xhr) {
      requests.push(xhr);
    };
  })
  afterEach(function() {
    xhr.restore();
  });
  describe("Action: checkUsername", () => {   
    it("Should call dispatch CHANGE_USERNAME_ERROR.", () => {
      Actions.checkUsername("foo@bar")(dispatchSpy)      
      const body = "不能含有特殊字符"
      
      // 手动设置 ajax response      
      requests[0].respond(200, {"Content-Type": "text/plain"}, body)  
          
      expect(actions[0]).to.have.property("type", Actions. CHANGE_USERNAME_ERROR)
      expect(actions[0]).to.have.property("error", "不能含有特殊字符")
    }) 
  })
})

reducer 就是一个普通函数 (state, action) => newState, 测试方法参考第三部分