Setup environment for testing React components with mocha, sinon, enzyme and jsdom

testSetup.js

/* This file helps you to setup an environment
 * for testing a React app with Mocha.
 * It provides transpiling and some global variables before
 * Mocha runs all the tests.
 * Usage example in npm script: "test": "mocha --require tools/testSetup.js test/*.test.js"
 * The major part of this file I got from Cory House pluralsight-redux-starter repo:
 * https://github.com/coryhouse/pluralsight-redux-starter/blob/master/tools/testSetup.js
 */

process.env.NODE_ENV = 'test';

/*
 * if tests are running without webpack,
 * register babel so that it will transpile ES6 to ES5 before our tests run.
 * I make it in mocha.opts file.
 * code: require('babel-register')();
 */

import sinon from 'sinon';
import expect from 'expect'; // import here your assertion library
import enzyme from 'enzyme';
import Adapter from 'enzyme-adapter-react-16';

enzyme.configure({ adapter: new Adapter() });

/*
 * if you use css modules with sass and would like test css classes
 */
import hook from 'css-modules-require-hook';
import sass from 'node-sass';

hook({
  extensions: [ '.scss', '.css' ],
  generateScopedName: '[local]__[hash:base64:8]', //your preferred generated className
  preprocessCss: ( data, file ) => sass.renderSync({ file }).css
});
//if you don't test styles, add next line (commented)
//require.extensions['.scss'] = function () {return null;}


// Disable webpack-specific features for tests since
// Mocha doesn't know what to do with them.
require.extensions['.png'] = function () {return null;};
require.extensions['.jpg'] = function () {return null;};

//add .svg right comprehension to mocha tests
import fs from 'fs';
require.extensions['.svg'] = function (module, filename) {
   module.exports = fs.readFileSync(filename, 'utf8');
};

global.sinon = sinon;
global.expect = expect;

global.navigator = {
    userAgent: 'node.js'
};