Install composer phpunit v9 for development testing

vendor/nikic/php-parser/lib/PhpParser/NodeTraverserInterface.php

@@ -0,0 +1,29 @@
+<?php declare(strict_types=1);
+
+namespace PhpParser;
+
+interface NodeTraverserInterface
+{
+    /**
+     * Adds a visitor.
+     *
+     * @param NodeVisitor $visitor Visitor to add
+     */
+    public function addVisitor(NodeVisitor $visitor);
+
+    /**
+     * Removes an added visitor.
+     *
+     * @param NodeVisitor $visitor
+     */
+    public function removeVisitor(NodeVisitor $visitor);
+
+    /**
+     * Traverses an array of nodes using the registered visitors.
+     *
+     * @param Node[] $nodes Array of nodes
+     *
+     * @return Node[] Traversed array of nodes
+     */
+    public function traverse(array $nodes) : array;
+}