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

vendor/phpunit/phpunit-mock-objects/tests/_fixture/MethodCallback.php

@@ -0,0 +1,21 @@
+<?php
+class MethodCallback
+{
+    public static function staticCallback()
+    {
+        $args = func_get_args();
+
+        if ($args == array('foo', 'bar')) {
+            return 'pass';
+        }
+    }
+
+    public function nonStaticCallback()
+    {
+        $args = func_get_args();
+
+        if ($args == array('foo', 'bar')) {
+            return 'pass';
+        }
+    }
+}