Regression Testing

The purpose of regression testing is to confirm that a  recent program or code change has not adversely affected existing features.

This testing is done to make sure that new code changes should not have side effects on the existing functionalities. It  ensures that old code still works once  the new code changes are done.
Regression Testing is required when there is a

• Change in requirements and code is modified according to the requirement
• New feature is added to the software
• Defect fixing
• Performance issue fix

Regression Testing Techniques

Software maintenance is an activity which includes enhancements, error corrections, optimization and deletion of existing features. These modifications may cause the system to work incorrectly . Therefore , Regression Testing becomes necessary. Regression Testing can be carried out using following techniques:

Regression Test Selection

• Instead of re-executing the entire test suite, it is better to select part of test suite to be run
• Test cases selected can be categorized as 1) Reusable Test Cases 2) Obsolete Test Cases.
• Re-usable Test cases can be used in succeeding regression cycles.
• Obsolete Test Cases can’t be used in succeeding cycles.

Selecting test cases for regression testing

It was found from industry data that good number of the defects reported by customers were due to last minute bug fixes creating side effects and hence selecting the test case for regression testing is an art and not that easy.  Effective Regression Tests can be done by selecting following test cases -

• Test cases which have frequent defects
• Functionalities which are more visible to the users
• Test cases which verify core features of the product
• Test cases of Functionalities which has undergone more and recent changes
• All Integration Test Cases
• All Complex Test Cases
• Boundary value test cases
• Sample of Successful test cases
• Sample of Failure test cases