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

One Column

[gallery columns="1"]

Two Columns

[gallery columns="2"]

Three Columns

[gallery columns="3"]

Four Columns

[gallery columns="4"]

Five Columns

[gallery columns="5"]

Six Columns

[gallery columns="6"]

Seven Columns

[gallery columns="7"]

Eight Columns

[gallery columns="8"]

Nine Columns

[gallery columns="9"]