diff --git a/core/modules/simpletest/src/TestDiscovery.php b/core/modules/simpletest/src/TestDiscovery.php
index e906ac9..3538934 100644
--- a/core/modules/simpletest/src/TestDiscovery.php
+++ b/core/modules/simpletest/src/TestDiscovery.php
@@ -141,7 +141,8 @@ public function registerTestNamespaces() {
    * @param string[] $types
    *   An array of included test types.
    *
-   * @return array An array of tests keyed by the first
+   * @return array
+   *   An array of tests keyed by the the group name.
    * @code
    *     $groups['block'] => array(
    *       'Drupal\block\Tests\BlockTest' => array(