The purpose of regression testing is to ensure that changes such as those mentioned above have not introduced new faults.[1] One of the main reasons for regression testing is to determine whether a change in one part of the software affects other parts of the software.

Common methods of regression testing include re-running previously completed tests and checking whether program behavior has changed and whether previously fixed faults have re-emerged. Regression testing can be performed to test a system efficiently by systematically selecting the appropriate minimum set of tests needed to adequately cover a particular change.