autotest, multiruby, and Test::Rails.
ZenTest scans your target and unit-test code and writes your missing
code based on simple naming rules, enabling XP at a much quicker
pace. ZenTest only works with Ruby and Test::Unit.
unit_diff is a command-line filter to diff expected results from
actual results and allow you to quickly see exactly what is wrong.
autotest is a continous testing facility meant to be used during
development. As soon as you save a file, autotest will run the
corresponding dependent tests.
multiruby runs anything you want on multiple versions of ruby.
Test::Rails helps you build industrial-strength Rails code.
WWW: http://zentest.rubyforge.org/