Undefined variable: classes Notice - simpletest.module - line 504 - simpletest_get_all_tests()

The code starting at line 504 reads:

  if (count($classes) == 0) {
    drupal_set_message('No test cases found.', 'error');
    return FALSE;
  }
  return $classes;
}

However $classes is not set in all code-paths. It either needs to be initialized at the top, or checked with !isset at the bottom. With this change, simpletest/tests/block.test goes "110 passes, 0 fails, and 0 exceptions" with E_ALL.

See attachment for the initialization approach.