White Screen on admin/build/tests

I installed the new version of the module, and immediately started getting white screens whenever I went to the test page. After throwing in a number of print_r statements to track down the cause, I discovered it happened when it was trying to include a test file written for the previous version of simpletest, which had a .test file extension, but used DrupalTestCase instead of DrupalWebTestCase - the include_once on the file was causing it to fail.

My temporary solution was to add a module_exists() check on the loop building the list of files to be included, but there's probably a better solution.