Update to drupal 8.0.0-rc1. For more information, see https://www.drupal.org/node/2582663

vendor/symfony/routing/Tests/Matcher/Dumper/DumperCollectionTest.php

@@ -0,0 +1,33 @@
+<?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\Routing\Tests\Matcher\Dumper;
+
+use Symfony\Component\Routing\Matcher\Dumper\DumperCollection;
+
+class DumperCollectionTest extends \PHPUnit_Framework_TestCase
+{
+    public function testGetRoot()
+    {
+        $a = new DumperCollection();
+
+        $b = new DumperCollection();
+        $a->add($b);
+
+        $c = new DumperCollection();
+        $b->add($c);
+
+        $d = new DumperCollection();
+        $c->add($d);
+
+        $this->assertSame($a, $c->getRoot());
+    }
+}