I was suffering with a problem running tests inside of textmate on a Rails 2 project, until I found this comment by David Vrensk at the bottom of this blog post by Rob Sanheim:

Posted by David Vrensk 18 January 2008 @ 9am

I think the easiest solution can be gleaned from the TM ticket that you link to (http://macromates.com/ticket/show?ticket_id=F4DA8B03). I just modify test/test_helper.rb in my current projects so that it starts with

$:.reject! { |e| e.include? ‘TextMate’ }

No patching the distros, and svn still works the way it should.