OK, create a file containing the following, and call it test.php.
<?php
class test extends Module
{
public function __construct()
{
$this->name = 'test';
$this->tab = 'Tools';
$this->version = "0.1";
parent::__construct();
/* The parent construct is required for translations */
$this->page = basename(__FILE__, '.php');
$this->displayName = $this->l('Test');
$this->description = $this->l('Just a test!');
}
function install()
{
if (!parent::install())
return false;
return true;
}
}
?>
Make a directory /modules/test and put the above file in it, and it should show up in the back office 
The $this->name member variable must match the directory and filename (case sensitive). The Class name must also match, but isn’t case sensitive.
Paul