--- /dev/null
+<?php
+
+namespace Drupal\early_rendering_controller_test;
+
+use Drupal\Core\Render\AttachmentsInterface;
+use Drupal\Core\Render\AttachmentsTrait;
+use Symfony\Component\HttpFoundation\Response;
+
+class AttachmentsTestResponse extends Response implements AttachmentsInterface {
+
+ use AttachmentsTrait;
+
+}