diff -u b/core/modules/simpletest/simpletest.module b/core/modules/simpletest/simpletest.module
--- b/core/modules/simpletest/simpletest.module
+++ b/core/modules/simpletest/simpletest.module
@@ -437,7 +437,7 @@
  *   returned.
  *
  * @return array[]
- *   An array of tests keyed with the groups specified in each of the tests
+ *   An array of tests keyed with the groups specified in each of the tests'
  *   getInfo() methods and then keyed by the test classes. For example:
  *   @code
  *     $groups['Block'] => array(