diff --git a/framework/core/tests/integration/extenders/RoutesTest.php b/framework/core/tests/integration/extenders/RoutesTest.php
new file mode 100644
index 000000000..f72569e8c
--- /dev/null
+++ b/framework/core/tests/integration/extenders/RoutesTest.php
@@ -0,0 +1,58 @@
+<?php
+
+/*
+ * This file is part of Flarum.
+ *
+ * For detailed copyright and license information, please view the
+ * LICENSE file that was distributed with this source code.
+ */
+
+namespace Flarum\Tests\integration\extenders;
+
+use Flarum\Extend;
+use Flarum\Tests\integration\TestCase;
+use Laminas\Diactoros\Response\TextResponse;
+use Psr\Http\Message\ResponseInterface;
+use Psr\Http\Message\ServerRequestInterface;
+use Psr\Http\Server\RequestHandlerInterface;
+
+class RoutesTest extends TestCase
+{
+    /**
+     * @test
+     */
+    public function custom_route_does_not_exist_by_default()
+    {
+        $response = $this->send(
+            $this->request('GET', '/custom')
+        );
+
+        $this->assertEquals(404, $response->getStatusCode());
+    }
+
+    /**
+     * @test
+     */
+    public function custom_route_can_be_added_by_extender()
+    {
+        $this->extend(
+            (new Extend\Routes('forum'))
+                ->get('/custom', 'custom', CustomRoute::class)
+        );
+
+        $response = $this->send(
+            $this->request('GET', '/custom')
+        );
+
+        $this->assertEquals(200, $response->getStatusCode());
+        $this->assertEquals('Hello Flarumites!', $response->getBody());
+    }
+}
+
+class CustomRoute implements RequestHandlerInterface
+{
+    public function handle(ServerRequestInterface $request): ResponseInterface
+    {
+        return new TextResponse('Hello Flarumites!');
+    }
+}