diff --git a/tests/phpunit/tests/comment/walker.php b/tests/phpunit/tests/comment/walker.php
index 443ca0c1cf..504c5e3b0f 100644
--- a/tests/phpunit/tests/comment/walker.php
+++ b/tests/phpunit/tests/comment/walker.php
@@ -7,6 +7,13 @@
  */
 class Tests_Comment_Walker extends WP_UnitTestCase {
 
+	/**
+	 * Comment post ID.
+	 *
+	 * @var int
+	 */
+	private $post_id;
+
 	public function set_up() {
 		parent::set_up();
 
@@ -28,7 +35,7 @@ class Tests_Comment_Walker extends WP_UnitTestCase {
 		$comment_child  = get_comment( $comment_child );
 
 		$comment_walker   = new Walker_Comment();
-		$comment_callback = new Comment_Callback_Test( $this, $comment_walker );
+		$comment_callback = new Comment_Callback_Test_Helper( $this, $comment_walker );
 
 		wp_list_comments(
 			array(
@@ -49,7 +56,10 @@ class Tests_Comment_Walker extends WP_UnitTestCase {
 	}
 }
 
-class Comment_Callback_Test {
+class Comment_Callback_Test_Helper {
+	private $test_walker;
+	private $walker;
+
 	public function __construct( Tests_Comment_Walker $test_walker, Walker_Comment $walker ) {
 		$this->test_walker = $test_walker;
 		$this->walker      = $walker;