Regression testing is a type of software testing that is performed to ensure that changes or updates made to an application or system do not cause unintended changes or problems to existing functionality. This type of testing involves running a set of previously passed test cases on the updated version of the software to ensure that all existing functionality still works as expected. Regression testing is typically performed at different stages of the software development cycle, including during the development, testing and release phases, to ensure that the software continues to meet the desired quality standards. Identifying and fixing issues early in the development cycle reduces the cost and effort of fixing them.

See also quality assurance.