I spent some time getting PowerDNS on Rails to run on Ruby 1.9.1, which ended up being very easy due to the small amount of plugins & gems used by the project. The only change I had to make myself was to the acts_as_audited plugin, where the one-line fix got merged upstream.
The worst part of the process was getting the specs to run with rake spec. Using ./script/spec it worked on individual specs and on all the specs worked as advertised, but rake spec didn’t do anything.
After a lot of time spent in the debugger I wasn’t any wiser. The only difference was that in Ruby 1.8 the example groups were fully loaded, and in Ruby 1.9 they were empty. I gave up and started searching relentlessly for some information on the issue. I couldn’t find anything, until I found an indirect solution on the rspec wiki. It seems that if you have any versions of the test-unit gem after the 1.2.3 release installed, your Rails specs will simply not run. For me, removing test-unit 2.0.3 made the difference and the specs ran properly. PowerDNS on Rails has now joined the ranks of my Ruby 1.9 compatible projects.