if checkbox checked not working in Opencart

I need to add checkbox to order process in Opencart 1.5.6.4 and ask "if checkbox is checked".

I add this checkbox to template/checkout/confirm.tpl

<input type="checkbox" name="test">

When I use the condition in controller/checkout/confirm.php if (isset($_POST['test'])) this condition not working, it is always false even if checkbox is checked.

Is it possible to use another way to create a condition if the checkbox is checked?