Inline JavaScript (ES6) unit-tests with node, gulp, speckjs, babel & tape

gulpfile.js

require('babel-core/register');
var babel = require('babel-core');
var gulp = require('gulp');
var speckjs = require('speckjs');
var tape = require('tape');
var through = require('through2');

function requireFromBuffer(buffer) {
  var m = new module.constructor();
  m.paths = module.paths;
  m._compile(buffer.toString());
  return m.exports;
}

function compile() {
  return through.obj(function (file, enc, cb) {
    file.contents = new Buffer(babel.transform(file.contents.toString()).code);
    cb(null, file);
  });
}

function spec() {
  return through.obj(function (file, enc, cb) {
    speckjs.build({
      name: file.path,
      content: file.contents.toString()
    }, {
      testFW: 'tape',
      onBuild: function(output) {
        file.contents = new Buffer(output);
        cb(null, file);
      }
    });
  });
}

function test() {
  var files = [];
  return through.obj(function (file, enc, cb) {
    files.push(file.contents);
    cb(null, file);
  }, function(cb) {
    tape.createStream().pipe(process.stdout);
    files.forEach(requireFromBuffer);
    cb();
  });
};

gulp.task('default',  ['speck']);

gulp.task('speck', function() {
  return gulp.src('./src/*.js')
    .pipe(compile())
    .pipe(spec())
    .pipe(test());
});

package.json

{
  "version": "1.0.0",
  "scripts": {
    "test": "gulp"
  },
  "author": "",
  "license": "ISC",
  "devDependencies": {
    "babel-core": "^5.8.24",
    "gulp": "^3.9.0",
    "speckjs": "^1.1.0",
    "tape": "^4.2.0",
    "through2": "^2.0.0"
  }
}

total.js

// ./src/total.js
/**
  total :: Num a => [a] -> a
  test > total function
  # total([1, 2]) == 3 (returns the sum of array)
  # total([3, 4, -5]) == 2 (works with negative numbers)
  # total([]) == 0 (works with an empty array)
  # total() == 0 (works with no arguments)
*/
export function total(x = []) {
  return x.reduce((x, y) =>  x + y, 0);
}