Custom rewrite not working

Try to add this one

function add_rewrite_rules() {
    $newrules = array('^testrewrite/([0-9]+)/?'=> 'index.php?page_id=$matches[1]');

    return $newrules ;
}
add_filter('rewrite_rules_array', 'add_rewrite_rules');

Let me know it is working or not.