As it turns out it was the jeweler gem that was the culprit for those Test::Unit::Errors. After removing that more of my tests started to work again, so I tried running the tests for mongomapper with ironruby. result: 100% pass rate. But it takes ironruby about 8x longer than it takes MRI (not the mingw version) results can be found here http://gist.github.com/319689 <http://gist.github.com/319689>this test was run on windows 7 x64 When trying to use ir64 I got the following output (master) ? ir64 -Itest -S testrb test/**/test_*.rb IronRuby.Libraries:0:in `Reinitialize'': Win32API is not supported in 64-bit process (System::NotSupportedException) from C:/ironruby/lib/ruby/site_ruby/1.8/rubygems/config_file.rb:48 from :0:in `require'' from C:/ruby-dist/bin/testrb:9 from :0:in `require'' If I read that correctly it''s not possible to run anything that uses gems in 64-bit mode --- Met vriendelijke groeten - Best regards - Salutations Ivan Porto Carrero Web: http://whiterabbitconsulting.eu - http://flanders.co.nz Twitter: http://twitter.com/casualjim Author of IronRuby in Action (http://manning.com/carrero) Microsoft IronRuby/C# MVP -------------- next part -------------- An HTML attachment was scrubbed... URL: <http://rubyforge.org/pipermail/ironruby-core/attachments/20100302/b7154901/attachment.html>