Test::Unit 2.x - Improved version of Test::Unit bundled
in Ruby 1.8.x. Ruby 1.9.x bundles minitest not Test::Unit.

Test::Unit bundled in Ruby 1.8.x had not been improved but
unbundled Test::Unit (Test::Unit 2.x) will be improved actively. 

WWW: http://test-unit.rubyforge.org/