For teams following agile software development practices, regression testing is a must. Agile teams constantly make changes to live software that can introduce regressions (or, code changes that break the functionality of part of an app). Regression testing can keep teams from shipping critical bugs to production by confirming the most important parts of an app are still working every time new code is pushed.

Regression Testing, as all Quality Assurance professionals know, is ensuring that previously developed and tested software continues to operate after a change. Performance Regression being a subset of regression testing as a discipline is therefore ensuring that previously developed and tested continues to meet its performance criteria after a change.