Handlers type checks added

src/Http/Handler.php

@@ -4,6 +4,7 @@
 namespace Reaponse\Http;
 
 
+use InvalidArgumentException;
 use Reaponse\ObjectStorage;
 use SplQueue;
 
@@ -27,6 +28,12 @@ public function __construct(array $handlers, ResponseInterface $response)
         $this->response = $response;
         $this->handlers = new SplQueue();
         foreach ($handlers as $handler) {
+            //make sure that all handlers implement HandlerInterface
+            if (!$handler instanceof HandlerInterface) {
+                $strHandler = get_class($handler);
+                throw new InvalidArgumentException("Handler {$strHandler} must implement Reaponse\Http\HandlerInterface");
+            }
+
             $this->handlers->push($handler);
         }
 

src/Http/Middleware.php

@@ -4,6 +4,7 @@
 namespace Reaponse\Http;
 
 
+use InvalidArgumentException;
 use Nette\Utils\JsonException;
 use Psr\Http\Message\ServerRequestInterface;
 use React\Promise\Deferred;
@@ -20,6 +21,10 @@ class Middleware
      */
     public function __construct(...$handler)
     {
+        if (empty($handler)) {
+            throw new InvalidArgumentException('Server handlers must be provided.');
+        }
+
         $this->handlers = $handler;
     }
 
@@ -34,7 +39,14 @@ public function __invoke(ServerRequestInterface $request): PromiseInterface
         $promise = $deferred->promise();
         $response = new Response($deferred, $request, $this->handlers);
 
-        $this->handlers[0]->handle($response);
+        $handler = $this->handlers[0];
+
+        if (!$handler instanceof HandlerInterface) {
+            $handlerStr = get_class($handler);
+            throw new InvalidArgumentException("Handler {$handlerStr} must implement Reaponse\Http\HandlerInterface");
+        }
+
+        $handler->handle($response);
         return $promise;
     }
 }