It has come to our, SimpleTest module developers, attention that the tests are breaking at a rapid rate. Most of the tests that currently have issues passed when they were originally committed to the core. The list of tests that passed was used during the cleanup stages, but hasn't been changed since SimpleTest was added to core and stands as a record.
I previously posted "Core patches need to update tests as well" in preparation for SimpleTest becoming part of core. Sadly it doesn't appear it was heeded.
After a long process of trial and error rolling back commits, webchick found the patch that broke the translation test, and possibly others. This would have saved everyone involved a lot of time had those who reviewed and wrote the patch simply run the tests on the patch, or better yet if testing.drupal.org were finished and implemented on drupal.org so that it would happen automatically.
Regardless it is rather annoying to spend several weeks cleaning up the tests to see them broken by un-tested commits. Before marking a patch as "ready to be committed" ensure that someone has run the suite of tests on it. If that hasn't been done I would hope that the patch isn't committed.