Regression Testing

As some one has said, changes are the only thing constant in this world. It holds true for software also, existing software are either being changed or removed from the shelves. These changes could be due to any reason. There could be some critical defects which needs to be fixed, there could be some enhancements which has to happen in order to remain in the competition. Regression testing is done to ensure that enhancement, defect fixes or any other changes made to the software has not broken any existing functionality.

Regression testing is very important, because in most places these days iterative development is used. In iterative development, shorter cycle is used with some functionality added in every cycle. In this scenario, it make sense to have regression testing for every cycle to make sure that new features are not breaking any existing functionality. Whenever there are any changes in the system, regression testing is performed. Regression testing can be performed for the complete product or it can be selective. Normally, full regression cycle is executed during the end of testing cycle and partial regression cycle is executed between the test cycles. During the regression cycle it becomes very important to select the proper test cases to get the maximum benefits. Test cases for regression testing should be selected based on the knowledge of
What defect fixes, enhancement or changes have gone into the system?
What is the impact of these changes on the other aspect of system?
Focus of the regression testing is always on the impact of the changes in the system. In most of the organizations, priority of the regression defect is always very high. It is normally included in the exit criteria of the product that it should have zero regression defects. Regression testing should always happen after the sanity or smoke testing. Sanity/Smoke can be defined as the type of testing which make sure that software is in testable state. Normally, sanity test suite will contain very basic and core test cases. These test cases decides the quality of the build and any failure in the sanity test suite should result in the rejection of build by the test team. Regression testing is a continuous process and and it happens after every release. Test cases are added to the regression suite after every release and repetitively executed for every release. Because test cases of regression suite are executed for every release, they are perfect candidate for the automation. Test automation is discussed separately in the Test Automation section of this website.