Abstract
This article explores testing as research site in the sociology of technology. A fully generalizable analysis is offered of testing in terms of a notion of projection. Prospective, current, and retrospective testing are identified The article is illustrated with examples of testing a clinical budgeting system in the United Kingdom National Health Service and the testing of the O-rings on the space shuttle Challenger. Lastly, the theme of "testing the user" is developed Some comments are offered on the pervasiveness of testing in society at large.