A webpack.config to run jest tests after compile

webpack.config.js

const { spawn } = require('child_process');

module.exports = {
  entry: {
    // ...
    // add this to let webpack watch on the test files changes
    tests: './test/path-to-the-tests-entry.js'
  },
  // ..
  plugins: [
    {
      // add a custom webpack plugin. For more info: https://webpack.js.org/concepts/plugins/
      apply: compiler => {
        // add a hook to run a callback after each compile
        compiler.hooks.afterCompile.tap('jest', compilation => {
          // run `npm test` using `spawn` to keep the format of the terminal just like you run it manually.
          // for more info: https://stackoverflow.com/a/20145153/863110
          spawn('npm', ['test'], {stdio:'inherit'});
        });
      }
    }
  ]
}