As discussed before, regression testing is performed in case of bug-fixing or whenever there is a need to incorporate any new requirements in the software. After the first release, whenever there is a a need to fix the bugs that have been reported or if there is any updation in the requirement itself, the developer fixes the bug or incorporates the new requirement by changing the code somewhere.

This changed software requires to be fully tested again so as to ensure: (a) bug-fixing has been carried out successfully, (b) the modifications have not affected other unchanged modules, and (c) the new requirements have been incorporated correctly (see Fig1). It means that every time you make a change in the software for whatever reasons, you have to perform a set of regression tests to validate a the software. This process of executing the whole set of tests and again may be time-consuming and frustrating, but it increases the quality of software. Therefore, the creation, maintenance, and execution of a regression test suite helps to retain the quality of the software. The importance of regression testing is well-understood for the following reasons:

• It validates the parts of the software where changes occur.
• It validates the parts of the software which may be affected by some changes, but otherwise unrelated.
• It ensures proper functioning of the software, as it was before changes occurred.
• It enhances the quality of software, as it reduces the risk of high-risk bugs.