gulpfile.babel.js

import gulp from 'gulp';
import ts from 'gulp-typescript';
import babel from 'gulp-babel';
import mocha from 'gulp-spawn-mocha';

gulp.task('build', () => {
  return gulp.src(['typings/tsd.d.ts', 'src/**/*.ts', 'test/**/*.ts'])
    .pipe(ts({
      target: 'ES6',
      outDir: 'build'
    }))
    .pipe(babel())
    .pipe(gulp.dest('build'))
  ;
});

gulp.task('test', ['build'], () => {
  return gulp.src('build/test/**/test_*.js', {read: false})
    .pipe(mocha({
      reporter: 'list',
      require: ['babel-core/polyfill']
    }));
});