Rails3-Bug6566 is a project mainly written in RUBY and JAVASCRIPT, it's free.
How to reproduce Rails Lighthouse Bug #6566
Download source from git://github.com/joeytheman/Rails3-Bug6566.git .
Run "bundle install".
Run "rake db:schema:load".
Navigate to "/users" and create 2 users.
Navigate to "/team" and create a new team with 2 teammates with the following parameters -Teammate 1 -- User => 1 -- Team => nil -- Position => "C" -Teammate 2 -- User => 2 -- Team => nil -- Position => "A"
Navigate to "/team/1/edit".
Set the position of player 1 to "A" and the position of player 2 to "C".
Attempt to save.