rcov is a tool for simple code coverage analysis in Ruby.

It features:

* fast execution: 20-300 times faster than previous tools
* multiple analysis modes
* fairly accurate coverage information through code linkage
  inference using simple heuristics
* XHTML and several kinds of text reports
* easy automation with Rake via a RcovTask
* colorblind-friendliness

WWW: http://eigenclass.org/hiki.rb?rcov