Fix assertInternalType deprecation in phpunit 9

Author: jderusse

Tests/Definition/Builder/TreeBuilderTest.php

@@ -12,11 +12,14 @@
 namespace Symfony\Component\Config\Tests\Definition\Builder;
 
 use PHPUnit\Framework\TestCase;
+use Symfony\Bridge\PhpUnit\ForwardCompatTestTrait;
 use Symfony\Component\Config\Definition\Builder\TreeBuilder;
 use Symfony\Component\Config\Tests\Fixtures\Builder\NodeBuilder as CustomNodeBuilder;
 
 class TreeBuilderTest extends TestCase
 {
+    use ForwardCompatTestTrait;
+
     public function testUsingACustomNodeBuilder()
     {
         $builder = new TreeBuilder();
@@ -128,7 +131,7 @@ public function testDefinitionExampleGetsTransferredToNode()
         $tree = $builder->buildTree();
         $children = $tree->getChildren();
 
-        $this->assertInternalType('array', $tree->getExample());
+        $this->assertIsArray($tree->getExample());
         $this->assertEquals('example', $children['child']->getExample());
     }
 }