Regression Testing is a type of testing that is done to verify that a code change in the software does not impact the existing functionality of the product. This is to make sure the product works fine with new functionality, bug fixes, or any change in the existing feature. Previously executed test cases are re-executed in order to verify the impact of change.

When To Perform This Test?

Regression Testing is usually performed after verification of changes or new functionality. But this is not the case always. For the release that is taking months to complete, regression tests must be incorporated in the daily test cycle. For weekly releases, regression tests can be performed when the Functional Testing is over for the changes.

Regression checking is a variation of retest (which is simply to repeat a test). When Retesting, the reason can be anything. Say, you were testing a particular feature and it was the end of the day- you could not finish testing and had to stop the process without deciding if the test passed/failed.

The next day when you come back, you perform the test once more – that means you are repeating a test you performed before. The simple act of repeating a test is a Retest.

Regression test at its core is a retest of sorts. It is only for the special occasion that something in the application/code has changed. It might be code, design or anything at all that dictates the overall framework of the system.

A Retest that is conducted in this situation to make sure that the said change has not made an impact on anything that was already working before is called Regression Test. The most common reasons why this might be conducted are because new versions of the code have been created (increase in scope/requirement) or bugs have been fixed.

Types Of Regression Testing :

1) Unit Regression :

Unit Regression is done during the Unit Testing phase and code is tested in isolation i.e. any dependencies on the unit to be tested are blocked so that the unit can be tested individually without any discrepancy.

2) Partial Regression :

Partial Regression is done to verify that the code works fine even when the changes have been done in the code and that unit is integrated with the unchanged or already existing code.

3) Complete Regression :

Complete Regression is done when a change in the code is done on a number of modules and also if the change impact of a change in any other module is uncertain. The product as a whole is regressed to check any changes because of the changed code.

Conclusion :

Regression Testing is one of the important aspects as it helps to deliver a quality product by making sure that any change in the code whether it’s small or large does not affect the existing or old functionality.