makegreen.vim is a vim (http://www.vim.org) plugin that runs make and shows the test run status with a red or green bar.
Copy all files to your ~/.vim directory or use Tim Pope's excellent pathogen plugin (http://github.com/tpope/vim-pathogen).
:MakeGreen % will run make for the current file and show its status with a red or green message bar.
example:
$ cd <your rails/merb root>
$ vim test/unit/user_test.rb
:compiler rubyunit
:MakeGreen %
See the full documentation for more.