diff -u b/core/modules/system/lib/Drupal/system/Tests/Theme/ThemeTestTwig.php b/core/modules/system/lib/Drupal/system/Tests/Theme/ThemeTestTwig.php
--- b/core/modules/system/lib/Drupal/system/Tests/Theme/ThemeTestTwig.php
+++ b/core/modules/system/lib/Drupal/system/Tests/Theme/ThemeTestTwig.php
@@ -74,8 +74,6 @@
    * Tests that the Twig engine handles PHP data correctly.
    */
   function testTwigVariableDataTypes() {
-    // Test NULL values.
-    // @todo Test multiple PHP data types.
     config('system.theme')
       ->set('default', 'test_theme_twig')
       ->save();
diff -u b/core/modules/system/tests/themes/test_theme_twig/theme_test.template_test.html.twig b/core/modules/system/tests/themes/test_theme_twig/theme_test.template_test.html.twig
--- b/core/modules/system/tests/themes/test_theme_twig/theme_test.template_test.html.twig
+++ b/core/modules/system/tests/themes/test_theme_twig/theme_test.template_test.html.twig
@@ -8 +8 @@
-</ul>
\ No newline at end of file
+</ul>