usability engineering
My perspective:
The usability engineering practices I have employed consist primarily of heuristic evaluations drawn from of the principles of Jakob Nielsen and formal testing models fashioned after Steve Krug & Mark Pearrow.
Thorough usability studies ensure that the product will meet the needs of the users by evaluating the information architecture and user acceptance assumptions. The results of the study either affirm, reject or modify the user experience.
In order to test the integrity of the information architecture, I have found it productive to actually observe representative users as they interact with the proposed organization and flow of information. In addition, I have also tested applications that I have not had a hand in planning. Testing for these projects usually involves a preliminary heuristic evaluation which is followed by task based user testing.