Testing React App written with ES6 with Mocha

npm install --save-dev mocha babel-register

Also make sure that you have valid .babelrc file.

{
  "presets": ["es2015", "react"],
  "plugins": ["transform-object-assign"]
}

And in the package.json,

...
"scripts": {
  "test": "mocha --compilers js:babel-register --recursive",
...

And just run npm test command.