Call to a member function sess_save() on a non-object

I think I found the issue, I removed the session driver from my autoload, but it looks like MY_Controller is being loaded, which has a bunch of calls to the session driver on the web site to handle things (login session, user identification). 

Seems like there needs to be a session testing driver that could be load in place of the cookie driver to work for unit testing. Otherwise there's no way to test any methods that use the Session driver without running into this.