diff -u b/core/modules/layout_builder/tests/src/FunctionalJavascript/FieldValuesTest.php b/core/modules/layout_builder/tests/src/FunctionalJavascript/FieldValuesTest.php
--- b/core/modules/layout_builder/tests/src/FunctionalJavascript/FieldValuesTest.php
+++ b/core/modules/layout_builder/tests/src/FunctionalJavascript/FieldValuesTest.php
@@ -27,12 +27,12 @@
   /**
    * {@inheritdoc}
    */
-  protected $defaultTheme = 'stark';
+  protected $defaultTheme = 'classy';
 
   /**
    * {@inheritdoc}
    */
-  protected function setUp() {
+  protected function setUp(): void {
     parent::setUp();
 
     $this->createContentType(['type' => 'bundle_for_testing_fields']);