These uses can be assembled into a sequence of uses, and the collection identified as a stochastic process subject to evaluation using statistical methods. Coverage testing is anecdotal and can only provide confidence about the specific paths tested. No assessment can be made about the paths not tested. Because usage testing exercises the software the way the users intend to use it, high-frequency errors tend to be found early. For this reason, statistical usage testing is more effective at improving software reliability than is coverage testing.
Coverage testing is as likely to find a rare execution failure as it is to find a frequent one.
As such, it must have a rigorous foundation. In other engineering disciplines, failures are neither expected nor accepted as normal. Other engineering professions have minimized error by developing a sound theoretical base on which to build design practices. Cleanroom methods provide a theoretical foundation for a comprehensive engineering process that has been reduced to practice for commercial software development. It also requires discipline.