Steve Krug calls it "Lost Our Lease Usability Testing" and explains how to do it in Don't Make Me Think. You can download the relevant chapters here: http://www.sensible.com/downloads-dmmt.html
We did this at a company I worked at a few years ago and it made us completely change how we were building the product because our target users got nothing out of it (I talked a bit about this a RubyFringe: http://www.infoq.com/presentations/francl-testing-overrated)