bundle.js

var pathmodify = require('pathmodify')
var browserify = require('browserify')

browserify('./index.js')
	.plugin(pathmodify(), {
		mods: [
			pathmodify.mod.dir('foo', './test/foo')
		]
	})
	.bundle();

index.js

var bar = require('foo/bar');

bar();

test-foo-bar.js

// put this in subdir ./test/foo

module.exports = function() {
	console.log('bar');
}