--- /dev/null
+<?php
+
+namespace Drupal\system_test\Controller;
+
+use Drupal\Core\Cache\CacheableJsonResponse;
+use Drupal\Core\Cache\CacheableResponse;
+use Symfony\Component\HttpFoundation\Request;
+
+/**
+ * Defines a controller to respond the page cache accept header test.
+ */
+class PageCacheAcceptHeaderController {
+
+ /**
+ * Processes a request that will vary with Accept header.
+ *
+ * @param \Symfony\Component\HttpFoundation\Request $request
+ * The current request object.
+ *
+ * @return mixed
+ */
+ public function content(Request $request) {
+ if ($request->getRequestFormat() === 'json') {
+ return new CacheableJsonResponse(['content' => 'oh hai this is json']);
+ }
+ else {
+ return new CacheableResponse("<p>oh hai this is html.</p>");
+ }
+ }
+
+}