title: running single rails unit/functional test
body: <p>As title. </p>
  
  <p>ruby test/functionals/whatevertest.rb doesn't work, that requires me to replace all <code>require 'test_helper'</code> to <code>require File.dirname(__FILE__) + '/../test_helper'</code>. For some reason most of those test templates have such issue, so I rather to see if there is a hack I could get around it.</p>