Unable to make shortcode, what is wrong?

That simply is too late for a shortcode. Just try putting it in your themes functions.php file.

Aside from that, using shortcodes imo are not a good idea. When you decide to change it, it will still stay in the database. This means either going through all places in the DB to clean up the now abandoned shortcode, cluttering your content (and wherever else you enabled the use of shortcodes) with [test] or disabling it by replacing the shortcode with something like an empty string, which means a massive parsing overhead.