From: Ryan Davis <ryand-ruby@...>
Date: 2007-12-28T03:47:13+09:00
Subject: Compatibility Testing for 1.9 using ZenTest's multiruby

If you've got a library or three, multiruby is an easy way to verify  
compatibility of multiple versions of ruby:

http://blog.zenspider.com/archives/2007/12/testing_for_ruby_18_and_19_using_multiruby.html