Check that factory returns an instance of LoopDriver

Author: kelunik

src/Loop.php

@@ -54,15 +54,21 @@ public static function execute(callable $callback, LoopDriver $driver = null)
     /**
      * Create a new driver if a factory is present, otherwise throw.
      *
-     * @throws \LogicException if no factory is set
+     * @throws \LogicException if no factory is set or no driver returned from factory
      */
     private static function createDriver()
     {
         if (self::$factory === null) {
             throw new \LogicException("Can't create an event loop driver without a factory.");
         }
 
-        return self::$factory->create();
+        $driver = self::$factory->create();
+
+        if (!$driver instanceof LoopDriver) {
+            throw new \LogicException("LoopDriverFactory didn't return a LoopDriver.");
+        }
+
+        return $driver;
     }
 
     /**