diff --git a/core/lib/Drupal/Core/Test/TestDatabase.php b/core/lib/Drupal/Core/Test/TestDatabase.php
index 7108514..9bfa25d 100644
--- a/core/lib/Drupal/Core/Test/TestDatabase.php
+++ b/core/lib/Drupal/Core/Test/TestDatabase.php
@@ -116,7 +116,8 @@ protected function getTestLock() {
     do {
       $lock_id = mt_rand(10000000, 99999999);
       // If we're only running with a concurrency of 1 there's no need to create
-      // a test lock.
+      // a test lock file as there is no chance of the random number generated
+      // clashing.
       if (getenv('RUN_TESTS_CONCURRENCY') > 1 && @symlink(__FILE__, $this->getLockFile($lock_id)) === FALSE) {
         $lock_id = NULL;
       }