From 8abfce2091e9665af93a920aed246e3b04abc2aa Mon Sep 17 00:00:00 2001
From: Sam Light <sam@lightscale.co.uk>
Date: Wed, 10 Jun 2026 19:00:32 +0100
Subject: throw an exception when route handler does not return response

---
 src/BasicStrategy.php                       |  9 ++++++++-
 src/Exceptions/InvalidResponseException.php | 12 ++++++++++++
 2 files changed, 20 insertions(+), 1 deletion(-)
 create mode 100644 src/Exceptions/InvalidResponseException.php

diff --git a/src/BasicStrategy.php b/src/BasicStrategy.php
index 62bc48e..5043576 100644
--- a/src/BasicStrategy.php
+++ b/src/BasicStrategy.php
@@ -5,6 +5,7 @@ declare(strict_types=1);
 namespace Lightscale\Router;
 
 use Lightscale\Router\Contracts\Strategy;
+use Lightscale\Router\Exceptions\InvalidResponseException;
 use Lightscale\Router\Exceptions\NotFoundException;
 use Psr\Http\Message\RequestInterface;
 use Psr\Http\Message\ResponseInterface;
@@ -13,7 +14,13 @@ class BasicStrategy implements Strategy
 {
     public function runRoute(RouteCall $call): ResponseInterface
     {
-        return ($call->route->getHandler())($call);
+        $result = ($call->route->getHandler())($call);
+
+        if ($result instanceof ResponseInterface) {
+            return $result;
+        }
+
+        throw new InvalidResponseException();
     }
 
     public function notFound(RequestInterface $request): ResponseInterface
diff --git a/src/Exceptions/InvalidResponseException.php b/src/Exceptions/InvalidResponseException.php
new file mode 100644
index 0000000..98577a1
--- /dev/null
+++ b/src/Exceptions/InvalidResponseException.php
@@ -0,0 +1,12 @@
+<?php
+
+declare(strict_types=1);
+
+namespace Lightscale\Router\Exceptions;
+
+use RuntimeException;
+
+class InvalidResponseException extends RuntimeException
+{
+    protected $message = 'Does not return an instance of ResponseInterface';
+}
-- 
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