Pipe babel to nodeunit via gulp without writing transpiled files to disk

Question

I'm trying to run nodeunit tests with support of ES6 features. To make feature support wider I use Babeljs transpiler.

gulp.task('test', function() {
  return gulp.
    src('src/**/*.js').
    pipe(babel()).
    pipe(gulp.dest("/dev/null")). // I'd like to get rid of it
    pipe(nodeunit()).
    on('error', function() {
        this.emit('end');
    });
});

The issue is that I don't wan't to write transpiled files to disk, I just want to pass them to nodeunit task. If I remove pipe(gulp.dest("/dev/null")) it seems that pipe(babel()) does nothing or just outputs somewhere in the void. When gulp.dest is in place everything works fine except that it writes files I don't need. So, is it possible to avoid transpiled files writing? And how?

P. S. I know the following ways, but they don't suit me:

1. I can use io.js to get wider ES6 support
2. I can just delete files after tests are run