N°2651 rollback gitignore for lib tests dirs

Too dangerous ! We'll work properly on this but for 2.8

lib/symfony/framework-bundle/Tests/Functional/app/Serializer/bundles.php

@@ -0,0 +1,16 @@
+<?php
+
+/*
+ * This file is part of the Symfony package.
+ *
+ * (c) Fabien Potencier <fabien@symfony.com>
+ *
+ * For the full copyright and license information, please view the LICENSE
+ * file that was distributed with this source code.
+ */
+
+use Symfony\Bundle\FrameworkBundle\FrameworkBundle;
+
+return [
+    new FrameworkBundle(),
+];

lib/symfony/framework-bundle/Tests/Functional/app/Serializer/config.yml

@@ -0,0 +1,10 @@
+imports:
+    - { resource: ../config/default.yml }
+
+services:
+    _defaults: { public: true }
+    test.property_info: '@property_info'
+
+framework:
+    serializer: { enabled: true }
+    property_info: { enabled: true }