> npm init
> npm install --save-dev mocha  //開發者模式下有效，不會部署到服務器上

{
  "name": "testapplication",
  "version": "1.0.0",
  "description": "",
  "main": "index.js",
  "scripts": {
    "test": "mocha **/*.test.js"
  },
  "author": "",
  "license": "ISC",
  "devDependencies": {
    "mocha": "^5.2.0"
  }
}

let add = (a,b)=>a+b;


it("test add",()=>{
    var res =  add(11,22);
    if(res!=33){
      throw new Error(`Expected 33 ,but got ${res}`)
    }
});

> npm test

> mocha **/*.test.js



  ? test add

  1 passing (4ms)

let add = (a,b)=>a+b;


it("test add",()=>{
    var res =  add(11,55);
    if(res!=33){
      throw new Error(`Expected 33 ,but got ${res}`)
    }
});

> testapplication@1.0.0 test /Users/jackson/Desktop/testApplication
> mocha **/*.test.js

  1) test add

  0 passing (4ms)
  1 failing

  1) test add:
     Error: Expected 33 ,but got 66
      at Context.it (add.test.js:8:15)



npm ERR! Test failed.  See above for more details.

> npm install --save-dev nodemon
> nodemon --exec "npm test"

{
  "name": "testapplication",
  "version": "1.0.0",
  "description": "",
  "main": "index.js",
  "scripts": {
    "test": "mocha **/*.test.js",
    "test-watch": "nodemon --exec \"npm test\""
  },
  "author": "",
  "license": "ISC",
  "devDependencies": {
    "mocha": "^5.2.0"
  }
}

>npm run test-watch