My high school honors teacher only had open book tests. At the very beginning of the year he explained that books were there so we didn't have to memorize formulas and could use our time for actually learning how to think and do the work. The books never had anything more useful in them than the formulas for the tests he gave us. I think this is the perfect use of open book tests. He also happened to be the coolest teacher "EVAR"! He threw some (well, a large chunk of) sodium in a pond at another school and the cops were called and he talked them into pretending to cuff him and take him away just to freak out his class. LOL!
