Gulp, webpack and mocha tester

gulpfile.js

var gulp = require('gulp');
var webpack = require('webpack');
var path = require('path');
var fs = require('fs');
var DeepMerge = require('deep-merge');
var Mocha = require('mocha');


var deepmerge = DeepMerge(function(target, source) {
  if(target instanceof Array) {
    return [].concat(target, source);
  }
  return source;
});

// generic

var defaultConfig = {
  module: {
    loaders: [
      {test: /\.js$/, exclude: /node_modules/, loaders: ['babel'] }
    ]
  }
};

if(process.env.NODE_ENV !== 'production') {
  defaultConfig.devtool = '#eval-source-map';
  defaultConfig.debug = true;
}

function config(overrides) {
  return deepmerge(defaultConfig, overrides || {});
}

function mochaTest(file, cb) {
  var mocha = new Mocha;
  mocha.addFile(file);
  var runner = mocha.run();
  runner.on('end', function() {
    // mocha uses require to initialize it's suite. We are now watching the
    // file so the file needs to be deleted from the cache.
    // see https://github.com/mochajs/mocha/blob/master/bin/_mocha#L358
    delete require.cache[file];
    if (cb) { cb(); }
  });
}


// backend
var mochaTestFile = path.join(__dirname, 'build/test/test.js');

var nodeModules = {};
fs.readdirSync('node_modules')
  .filter(function(x) {
    return ['.bin'].indexOf(x) === -1;
  })
  .forEach(function(mod) {
    nodeModules[mod] = 'commonjs ' + mod;
  });

var testConfig = config({
  entry: './test/sanity_test.js',
  target: 'node',
  output: {
    path: path.join(__dirname, 'build/test'),
    filename: 'test.js'
  },
  node: {
    __dirname: true,
    __filename: true
  },
  externals: nodeModules,
  plugins: [
    new webpack.IgnorePlugin(/\.(css|less)$/),
    new webpack.BannerPlugin('require("source-map-support").install();',
                             { raw: true, entryOnly: false })
  ]
});

// tasks

function onBuild(done) {
  return function(err, stats) {
    if(err) {
      console.log('Error', err);
    }
    else {
      console.log(stats.toString());
    }

    if(done) {
      done();
    }
  };
}

gulp.task('test-build', function(done) {
  webpack(testConfig).run(function(err, stats) {
    onBuild()(err, stats);
    mochaTest(mochaTestFile, done);
  });
});

gulp.task('test-watch', function() {
  webpack(testConfig).watch(100, function(err, stats) {
    onBuild()(err, stats);
    mochaTest(mochaTestFile);
  });
});

based on https://github.com/jlongster/backend-with-webpack