Regression Testing is performed whenever a program or code undergoes a change to verify that the existing functionalities have not been affected. Even if a small change made to the code can bring unexpected issues. To ensure that the new code changes have no side effects on the existing features, regression testing is done.
Regression testing becomes important whenever there are any code changes due to change in requirements, or a new feature is added to the software. Software maintenance process includes error corrections, enhancements, optimization and deletion of existing features. These changes may cause the system to work incorrectly making regression testing important.