Guard
Due to a bug in the current guard-minitest version you should use this fork for now: https://github.com/grimen/guard-minitest :
$ git clone https://github.com/grimen/guard-minitest.git guard-minitest
$ cd guard-minitest
$ gem build guard-minitest.gemspec
$ cd ../path/to/spinaltap/gem
$ gem install ../path/to/guard-minitest/guard-minitest-0.4.0.gem