what is regression testing

Regression testing is a type of software testing that is conducted after a code update or change to ensure that the update has not introduced any new bugs or issues. It is an integral part of the software development process, particularly in the extreme programming software development method. Regression testing is performed after functional testing has concluded, to verify that the other functionalities are working. It can be achieved through multiple approaches, including retesting all, regression test selection, and test case prioritization. Regression testing can be used not only for testing the correctness of a program but often also for tracking the quality of its output. Visual regression testing is also employed to detect visual bugs that may occur due to changes in the codebase. Regression testing helps developers to focus their efforts on fixing the issues that have been introduced by the changes, rather than spending time on testing the entire software package.