I just recently received an update to TextMate. However, I discovered that I could no longer Run Focused Unit Test as it would complain:
in `check_gem_dependencies': undefined method `ruby_version' for Gem:Module (NoMethodError)
I got a clue when I noticed in the RubyMate window that the patch level of the ruby interpreter was different from the patch level of the ruby I use from a Terminal window. Clearly, TextMate was using a different Ruby executable than I was the rest of the time.
I poked around in the Ruby bundle a little bit and noticed references to a variable TM_RUBY. Looking around some more, I discovered in the Preferences under Advanced there is a Shell Variables tab. I added a TM_RUBY variable there and pointed it to the ruby I wanted it to use (/usr/local/bin/ruby in my case). Restarted TextMate, et voilà — Run Focused Unit Test works perfectly again.