diff --git a/core/tests/Drupal/Tests/Core/Lock/LockBackendAbstractTest.php b/core/tests/Drupal/Tests/Core/Lock/LockBackendAbstractTest.php
index 8a06108..2a424ed 100644
--- a/core/tests/Drupal/Tests/Core/Lock/LockBackendAbstractTest.php
+++ b/core/tests/Drupal/Tests/Core/Lock/LockBackendAbstractTest.php
@@ -23,7 +23,8 @@ class LockBackendAbstractTest extends UnitTestCase {
   protected $lock;
 
   protected function setUp() {
-    // Locks require a precision of at least 14.
+    // Set precision below required 14 to verify increase later on.
+    // @see \Drupal\Core\Lock\LockBackendAbstract::__construct().
     ini_set('precision', 12);
     $this->lock = $this->getMockForAbstractClass('Drupal\Core\Lock\LockBackendAbstract');
   }