Add tests

![http://media.tumblr.com/tumblr_m7or5ecmr41rter4a.gif](http://media.tumblr.com/tumblr_m7or5ecmr41rter4a.gif)

This project doesn't have any tests, so we should remedy that.
`[]` was recommended by the documentation.  I'll test None and see if it works :)