The application of computers to control either analogue or digital test techniques in order to evaluate the quality of components and products. Computer-aided testing is used to check that the component parts, subassemblies, and full systems are within specified tolerances and also perform up to specification. Note that performance to specification may require that the unit or system operates under stressful conditions that would not be encountered in normal use. The parameters (test criteria) for computer-aided testing are often derived from computer-aided design and computer-aided manufacturing systems.