Added docblocks and fixed a couple tests

src/Monolog/Formatter/JsonFormatter.php

@@ -13,11 +13,18 @@ namespace Monolog\Formatter;
 
 use Monolog\Logger;
 
+/**
+ * Encodes whatever message data is passed to it as json
+ *
+ * This can be useful to log to databases or remote APIs
+ *
+ * @author Jordi Boggiano <j.boggiano@seld.be>
+ */
 class JsonFormatter implements FormatterInterface
 {
     public function format($message)
     {
-        $message['message'] = json_encode($message['message']);
+        $message['message'] = json_encode($message);
         return $message;
     }
 }