Regression testing

What is regression testing? Why do it? What value does it have? My short answer to these questions is regression testing as a concept is about searching for new faults introduced through changes to the code base, and to learn more about the system you are building.

Usually in modern development, through an automated build pipeline, you are constantly executing checks that help detect whether the changes made to your code have resulted in new faults being introduced. Couple this with the interactive testing that we do throughout the development of any story then we have a combined effort that you could describe as regression testing.

In my mind, thats pretty much it. Its main purpose is to find faults, and learn more about the system.

Many people become confused about the term regression testing, and rightly question its worth when they judge either automated only solutions, typically through a UI or API, or look to have regression testing as a phase that occurs at some point on the critical path to delivery. Both of these approaches fall into the realm of delivery anti patterns.

If you think of your entire test and development approach as a way to minimise the risk of regression and to deliver the right thing in the most effective and safe way, you very rarely have to think about or understand the need for regression testing.

Thats my rather simplistic view. For more detail, have a read of Michael Bolton’s presentation "Things Could Get Worse: Ideas About Regression Testing"