installation-karma-mocha-chai.md

Set up Karma with Mocha and Chai in Create React App

This guide will use specific versions NPM packages. Please double-check that you installed the same versions to avoid installation issues!

1. Install Create React App

$ npm install -g [email protected]

2. Create a new React application and eject from it

$ create-react-app my-app
$ cd my-app
$ npm run eject

Press y to confirm that you want to eject.

3. Install Karma, Karma related libraries, and Babel Polyfill

$ npm i -D [email protected] [email protected] [email protected]
$ npm i -D [email protected] [email protected]

4. Install Chai, Mocha, and their Karma adapters

$ npm i -D [email protected] [email protected] [email protected] [email protected]

5. Install react-page-object, enzyme, and react-test-renderer

$ npm i -D react-page-object [email protected] [email protected]

6. Modify your package.json scripts to be

"scripts": {
  "start": "node scripts/start.js",
  "build": "node scripts/build.js",
  "test": "npm run karma -- --single-run",
  "karma": "BABEL_ENV=development NODE_ENV=test node_modules/karma/bin/karma start config/karma.conf.js"
},

7. Create a Karma configuration file

$ touch config/karma.conf.js

8. Add the following to your config/karma.conf.js file

var path = require('path');
var testHelperPath = path.resolve('test/testHelper.js')

module.exports = function(config) {
  config.set({
    // use the PhantomJS browser
    browsers: ['PhantomJS'],
    // use mocha and chai
    frameworks: ['mocha', 'chai'],

    // files that Karma will server to the browser
    files: [
      // entry file for Webpack
      testHelperPath
    ],

    // before serving test/testHelper.js to the browser
    preprocessors: {
      [testHelperPath]: [
        // use karma-webpack to preprocess the file via webpack
        'webpack',
        // use karma-sourcemap-loader to utilize sourcemaps generated by webpack
        'sourcemap'
      ]
    },

    // webpack configuration used by karma-webpack
    webpack: {
      // generate sourcemaps
      devtool: 'inline-source-map',
      // enzyme-specific setup
      externals: {
        'cheerio': 'window',
        'react/addons': true,
        'react/lib/ExecutionEnvironment': true,
        'react/lib/ReactContext': true
      },
      module: {
        // lint JavaScript with Eslint
        preLoaders: [
          {
            test: /\.(js|jsx)$/,
            exclude: /node_modules/,
            loader: 'eslint'
          }
        ],
        // use same loaders as Create React App
        loaders: [
          {
            exclude: [
              /\.(js|jsx)$/,
              /\.css$/,
              /\.json$/,
            ],
            loader: 'file',
            query: {
              name: 'static/media/[name].[hash:8].[ext]'
            }
          },
          {
            test: /\.(js|jsx)$/,
            exclude: /node_modules/,
            loader: 'babel'
          },
          {
            test: /\.css$/,
            loader: 'style!css'
          },
          {
            test: /\.json$/,
            loader: 'json'
          }
        ]
      },
      // relative path starts out at the src folder when importing modules
      resolve: {
        root: path.resolve('./src')
      }
    },

    webpackMiddleware: {
      // only output webpack error messages
      stats: 'errors-only'
    },
  })
}

9. In the application root folder, create a test folder and a testHelper.js file to it.

$ mkdir test
$ touch test/testHelper.js

10. Add the following to your test/testHelper.js file.

// polyfill PhantomJS environment
import 'babel-polyfill'
import 'whatwg-fetch'

// require all the test files in the test folder that end with Spec.js or Spec.jsx
const testsContext = require.context(".", true, /Spec.jsx?$/);
testsContext.keys().forEach(testsContext);

// output at when the test were run
console.info(`TESTS RAN AT ${new Date().toLocaleTimeString()}`);

11. Create a passing test file

$ touch test/AppSpec.js

12. Add the following content to test/AppSpec.js

import Page from 'react-page-object'
import React from 'react'
import App from 'App'

describe('AppSpec', function() {
  let page

  beforeEach(function() {
    page = new Page(<App />)
  })

  afterEach(function() {
    page.destroy()
  })

  it('should pass', function() {
    expect(page.content()).to.match(/Welcome to React/)
  })
})

At this point, the set up is complete! You can run all your tests once with

$ npm test

Or continuously with

$ npm run karma