Regression testing

What is Regression Testing?

Regression Testing is defined as a type of software testing to confirm that a recent code change has not adversely affected existing features.

Regression Testing is nothing but a full or partial selection of already executed test cases which are re-executed to ensure existing functionalities work fine.

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

The Need of Regression Testing

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

How to do Regression Testing

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 the following techniques:

Retest All

• This is one of the methods for Regression Testing in which all the tests in the existing test bucket or suite should be re-executed. This is very expensive as it requires huge time and resources.

Regression Test Selection

• Instead of re-executing the entire test suite, it is better to select part of the 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.

Prioritization of Test Cases

• Prioritize the test cases depending on business impact, critical & frequently used functionalities. Selection of test cases based on priority will greatly reduce the regression test suite.

Selecting Test Cases for Regression Testing

It was found from industry data that a 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 the 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

Difference between Re-Testing and Regression Testing:

Retesting means testing the functionality or bug again to ensure the code is fixed. If it is not fixed, Defect needs to be re-opened. If fixed, Defect is closed.

Regression testing means testing your software application when it undergoes a code change to ensure that the new code has not affected other parts of the software.