metamask-extension/test/integration/index.js

const fs = require('fs')
const path = require('path')
const browserify = require('browserify')
const tests = fs.readdirSync(path.join(__dirname, 'lib'))
const bundlePath = path.join(__dirname, 'bundle.js')

const b = browserify()

const writeStream = fs.createWriteStream(bundlePath)

tests.forEach(function (fileName) {
  b.add(path.join(__dirname, 'lib', fileName))
})

b.bundle()
.pipe(writeStream)
.on('error', (err) => {
  throw err
})