You can use this page to test the Theme's handling of the shortcode, including the <code>columns</code> parameter, from 1 to 9 columns. Themes are only required to support the default setting (3 columns), so this page is entirely optional.

[gallery size="medium" ids="3004,3003,3002,3001,2998,2987,2990,2994,2985,2986,2984,2981"]