N°2651 rollback gitignore for lib tests dirs

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

lib/symfony/http-kernel/Tests/DependencyInjection/MergeExtensionConfigurationPassTest.php

@@ -0,0 +1,50 @@
+<?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.
+ */
+
+namespace Symfony\Component\HttpKernel\Tests\DependencyInjection;
+
+use PHPUnit\Framework\TestCase;
+use Symfony\Component\DependencyInjection\ContainerBuilder;
+use Symfony\Component\HttpKernel\DependencyInjection\Extension;
+use Symfony\Component\HttpKernel\DependencyInjection\MergeExtensionConfigurationPass;
+
+class MergeExtensionConfigurationPassTest extends TestCase
+{
+    public function testAutoloadMainExtension()
+    {
+        $container = new ContainerBuilder();
+        $container->registerExtension(new LoadedExtension());
+        $container->registerExtension(new NotLoadedExtension());
+        $container->loadFromExtension('loaded', []);
+
+        $configPass = new MergeExtensionConfigurationPass(['loaded', 'not_loaded']);
+        $configPass->process($container);
+
+        $this->assertTrue($container->hasDefinition('loaded.foo'));
+        $this->assertTrue($container->hasDefinition('not_loaded.bar'));
+    }
+}
+
+class LoadedExtension extends Extension
+{
+    public function load(array $configs, ContainerBuilder $container)
+    {
+        $container->register('loaded.foo');
+    }
+}
+
+class NotLoadedExtension extends Extension
+{
+    public function load(array $configs, ContainerBuilder $container)
+    {
+        $container->register('not_loaded.bar');
+    }
+}