diff -u b/core/tests/Drupal/Tests/Core/Render/ProtectedRenderArrayTest.php b/core/tests/Drupal/Tests/Core/Render/ProtectedRenderArrayTest.php
--- b/core/tests/Drupal/Tests/Core/Render/ProtectedRenderArrayTest.php
+++ b/core/tests/Drupal/Tests/Core/Render/ProtectedRenderArrayTest.php
@@ -6,7 +6,7 @@
 use Drupal\Tests\UnitTestCase;
 
 /**
- * Confirm that the MetadataBubblingUrlGenerator is functioning properly.
+ * Tests that protected render arrays can not be modified.
  *
  * @coversDefaultClass \Drupal\Core\Render\ProtectedRenderArray
  *