摘要：可以監控文件變化自動執行單元測試，可以緩存測試結果，可以顯示測試過程中的變量測試框架。執行單元測試三測試在的理念中，組件應該分為視覺組件和高階組件，與邏輯分離，更利于測試。

karma：測試過程管理工具。可以監控文件變化自動執行單元測試，可以緩存測試結果，可以console.log顯示測試過程中的變量

mocha：測試框架。提供describe，it，beforeEach等函數管理你的 testcase，后面示例中會看到

chai：BDD（行為驅動開發）和TDD（測試驅動開發）雙測試風格的斷言庫

enzyme：React測試工具，可以類似 jquery 風格的 api 操作react 節點

sinon: 提供 fake 數據， 替換函數調用等功能

工具安裝就是 npm install，這里就不再詳述，主要的配置項目在karma.conf.js中，可以參考這個模板項目 react-redux-starter-kit 。如果項目中用到全局變量，比如jquery, momentjs等，需要在測試環境中全局引入，否則報錯，例如，在karma.conf中引入全局變量jQuery:

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

在test-bundler.js中設置全局的變量，包括chai, sinon等：

/* 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()

...

先熱身看看簡單的函數如何單元測試：

/* helpers/validator.js */

export function checkUsername (name) {
  if (name.length === 0 || name.length > 15) {
    return "用戶名必須為1-15個字"
  }
  return ""
}

/* 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("用戶名必須為1-15個字")
        })
        it("Should return error while more then 15 words.", () => {
            expect(Validators.checkUsername("abcdefghijklmnop")).to.equal("用戶名必須為1-15個字")
            expect(Validators.checkUsername("一二三四五六七八九十一二三四五六")).to.equal("用戶名必須為1-15個字")
        })
    })
})

describe可以多次嵌套使用，更清晰的描述測試功能的結構。執行單元測試:
babel-node ./node_modules/karma/bin/karma start build/karma.conf

在 redux 的理念中，react 組件應該分為視覺組件 component 和 高階組件 container，UI與邏輯分離，更利于測試。redux 的 example 里，這兩種組件一般都分開文件去存放。本人認為，如果視覺組件需要多次復用，應該與container分開來寫，但如果基本不復用，或者可以復用的組件已經專門組件化了(下面例子就是)，那就沒必要分開寫，可以寫在一個文件里更方便管理，然后通過 export 和 export default 分別輸出

/* 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
    

      
        用戶名
        
          
          請輸入用戶名
          {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)

測試 componet，這里用到 enzyme 和 sinon：

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函數在每個測試用例啟動前做一些初始化工作

enzyme shallow 的用法跟 jquery 的dom操作類似，可以通過選擇器過濾出想要的節點，可以接受 css 選擇器或者react class，如：find(".someClass")， find(TextInput)

這里用到了 sinon 的spies, 可以觀察到函數的調用情況。他還提供stub, mock功能，了解更多請 google

先來看一個普通的 action：

/* 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 就是一個簡單的函數，返回一個 object，測試起來跟前面的簡單函數例子一樣:

/* 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
    })   
  })
   
})

再來看一下異步 action, 這里功能是改變 username 的同時發起檢查:

export const CHANGE_USERNAME = "CHANGE_USERNAME"

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

測試代碼：

/* 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", "")
    }) 
  })
})

假如現在產品需求變更，要求實時在后臺檢查 username 的合法性, 就需要用到 ajax 了, 這里假設使用 Jquery 來實現 ajax 請求:

/* 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
      })
    })
  }
}

要測試 ajax 請求，可以用 sinon 的 fake XMLHttpRequest, 不用為了測試改動 action 任何代碼:

/* 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"
      
      // 手動設置 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 就是一個普通函數 (state, action) => newState, 測試方法參考第三部分