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)...

rcodetools 0.7.0 introduces "test-driven completion" (TDC) which allows 100%-accurate completion while alternating between implementation and tests. Several new mechanisms allow faster development in large projects, and xmpfilter supports RSpec's latest syntax.

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

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