Software engineering is the only engineering discipline where product testing is amajor technical and organizational concern, as well as an important cost factor.Several factors contribute to this state of affairs:• The first factor that makes software testing such a big concern is, of course, thesize and complexity of software products, which make the design of softwareproducts a high-risk, error-prone proposition.• The second factor is the lack of a standardized development process for softwareproducts, which means that product quality cannot be ensured by process controls,and has to be ensured by product controls instead.• The third factor is the scarcity of practical, scalable methods that can ensure productquality through static product analysis, shifting the burden to dynamicmethods.• Other factors include the absence of a general reuse discipline, the lack of scalabilityof correctness-preserving development methods, and the pervasiveness ofspecification changes through the development, maintenance, and evolutionprocess, etc.