I'm running Mac OS X Snow Leopard (10.6.4) with IDEA 9.0.3 (build IU-95.429) on Java 1.6.0_20 with RubyMine plugin 2.5.12197.
Previously I was running IDEA 9.0.2 and had no problems running Ruby Test::Unit::TestCase tests using either a new Run Configuration or the Run Context Menu option (Ctrl-Shift-F10 or right-click and select the Run "..." menu option.)
Now after upgrading to 9.0.3, whenever I try to run a Test::Unit::TestCase test using either a Run Configuration menu option or the Run Context menu shortcut, I see the "Make" icon appear briefly in the status bar and then see the status message "All files are up-to-date."
I don't see any messages in the idea.log nor are there any new thread dump folders that appear.
This happens on any existing Ruby or Rails projects, plus also on a brand new Rails project I created.