It seems to me that, as long as testing is an opt-in process, this problem won't go away. testing.drupal.org will make a huge difference, but perhaps we need another solution in the meantime.

One possibility: Instead of asking people not to mark patches as RTBC until tests are written and all tests have been run, perhaps its time to add some new steps to the issue workflow. Ie instead of going from CNR to RTBC, perhaps it should be CNR => CNTR (Code Needs Tests Run) => RTBC. In this case, at least committing a patch without running tests would be an explicit decision.

True, http://drupal.org/node/156119 already clearly says that RTBC shouldn't be used until testing has been performed, but clearly people haven't fully embraced that practice and, instead, see the transition from CNR to RTBC as largely a code-review step, not a review and test step.

Just a thought.