rcodetools is a collection of Ruby code manipulation tools for automagic Test::Unit(RSpec) assertion generation, code annotation, 100% accurate code completion, code and documentation browsing, precise method information (rcodetools is meta-programming aware)...

The ability to present information about the completion candidates was introduced in 0.5.0.

rcodetools can be used with any editor, but it ships with emacs and vim support.

More info at http://eigenclass.org/hiki.rb?rcodetools