No coverage information was collected, exit without writing coverage information es6

解决方法1：

有问题的branch：https://github.com/JakeSidSmith/istanbul-no-coverage
运行成功的branch：https://github.com/JakeSidSmith/istanbul-no-coverage/pull/1

   "scripts": {
      "start": "http-server . -c-1 -o",
      "build": "mkdir -p build/js/ && browserify -t babelify src/js/index.js -o build/js/index.js",
 -    "test": "istanbul cover node_modules/mocha/bin/_mocha -- --compilers js:babel-core/register --require test-helper.js --harmony --bail --recursive 'src/js/__tests__/**/*.test.js'"
 +    "test": "babel-node ./node_modules/istanbul/lib/cli cover node_modules/mocha/bin/_mocha -- --require test-helper.js --bail --recursive 'src/js/__tests__/**/*.test.js'"
    },
    "author": "",
    "license": "ISC",
 @@ -20,11 +20,12 @@
      "react-dom": "=0.14.2"
    },
    "devDependencies": {
 +    "babel-cli": "^6.2.0",
      "babel-core": "=6.2.1",
      "chai": "=3.4.1",
      "chai-immutable": "=1.5.3",
      "http-server": "=0.8.5",
 -    "istanbul": "=0.4.1",
 +    "istanbul": "^1.0.0-alpha",
      "jsdom": "=7.1.0",
      "mocha": "=2.3.4",
      "react-addons-test-utils": "=0.14.2",

测验有效，但是我istanbul版本是最新的"istanbul":"^0.4.5"，而且作者也说这种方法在其他版本里面可能会出现问题。

解决方法2：

使用babel-istanbul in lieu of istanbul

"test:coverage": "babel-node ./node_modules/.bin/babel-istanbul cover ./node_modules/.bin/_mocha ./src/**/__tests__/*.js"

stackoverflow原问题地址

Transformation error; return original code

创建一个.istanbul.yml文件，内容

instrumentation:
    root: src

或者在命令行添加 --root /src
在使用了babel-istanbul之后，这个问题不需要.istanbul.yml文件和命令行设置也可以工作了。

更多的讨论

Window is not defined

可以用jsdom-global来fix这个问题，介绍很清晰明了。

jsdom-global will inject document, window and other DOM API into your Node.js environment. Useful for running, in Node.js, tests that are made for browsers.

npm install --save-dev --save-exact jsdom jsdom-global

然后把-r jsdom-global/register加到mocha的command line里面。

最后我在package.json中的设置
"test-cov": "babel-node ./node_modules/.bin/babel-istanbul cover _mocha -- --recursive './frontend/**/*.test.js' -r jsdom-global/register"

运行结果：

25 passing (57ms)  

=============================== Coverage summary ===============================
Statements   : 81.96% ( 559/682 )
Branches     : 88.46% ( 150/169 ), 2 ignored
Functions    : 81.43% ( 114/140 )
Lines        : 80.67% ( 480/595 )
================================================================================