WP_UnitTest_Factory_For_Post::update_object PHP Method

    function update_object($post_id, $fields)
    {
        $fields['ID'] = $post_id;
        return wp_update_post($fields);
    }

 public function update_object($paper_id, $fields)
 {
     unset($fields['post_type']);
     return parent::update_object($paper_id, $fields);
 }