see example output here:
http://neoneye.dk/coverage/
download it from here: tgz, zip, gem.
http://rubyforge.org/project/showfiles.php?group_id=18&release_id=361
changes since 0.1
-
sidebar can be specified, by creating a file named 'coverage.sidebar'. -
avoid absolute names. -
output to the local dir 'coverage'. -
XHTML1.0 strict.
Purpose
···
=======
This tool helps identify those lines of code in your
program which didn’t got executed while running.
NaHi is the author of the original ‘coverage.rb’,
47 lines of Ruby code. Today it outputs nice HTML.
License
Ruby’s license
Install
Follow these 3 steps in order to install
ruby install.rb config
ruby install.rb setup
ruby install.rb install
Usage
Insert ‘-rcoverage’ when you wish to make coverage output.
For instance:
ruby -rcoverage test_all.rb
It should generage an ‘index.html’ file, containing coverage info.
Credits
NAKAMURA Hiroshi (NaHi) for the original coverage code.
Mauricio Julio Fernández Pradier, lots of improvements.
Robert Feldt, for suggestions.
end of document
sorry in advance for announcing this package twice 
–
Simon Strandgaard