Add content type headers

app/src/Controller/Controller.php

@@ -53,7 +53,9 @@ abstract class Controller
      */
     public function render(string $templateName, array $data = []): Response
     {
-        return $this->view->render($this->response, $templateName, $data);
+        return $this->view
+                    ->render($this->response, $templateName, $data)
+                    ->withHeader('Content-Type', 'text/html');
     }
 
     /**
@@ -65,7 +67,7 @@ abstract class Controller
     {
         $renderedTemplate = $this->view->fetchFromString($html, $data);
         $this->response->getBody()->write($renderedTemplate);
-        return $this->response;
+        return $this->response->withHeader('Content-Type', 'text/html');
     }
 
     /**

app/tests/Controller/ControllerTest.php

@@ -28,4 +28,29 @@ class ControllerTest extends TestCase
 
         $this->assertEquals('<p>Dave</p>', $response->getBody());
     }
+
+    public function testHtmlInlineResponseCodes(): void
+    {
+        $testController = new class extends Controller {
+            public function respond(): Response
+            {
+                $response = $this->renderInline(
+                    '<p>{{ name }}</p>',
+                    [ 'name' => 'Oh no!' ]
+                );
+
+                return $response->withStatus(400);
+            }
+        };
+
+        $app = $this->getAppInstance();
+        $app->get('/test', $testController);
+
+        $request = $this->createRequest('GET', '/test');
+        $response = $app->handle($request);
+
+        $this->assertEquals(400, $response->getStatusCode());
+        $this->assertEquals('<p>Oh no!</p>', $response->getBody());
+        $this->assertEquals('text/html', $response->getHeaderLine('Content-Type'));
+    }
 }