Key Takeaways
Regression testing verifies that existing functionality still works after a code change. The change might be a bug fix, a new feature, a refactor, or a dependency update — all of them carry the risk of breaking something that was working.
The types differ in scope: corrective regression is lightweight and reuses existing tests, complete regression covers the whole system, selective regression targets only affected areas. Choosing the right type based on the size of the change matters.
Automation is what makes regression testing sustainable. Manual regression on a large application is slow and expensive. Automated suites that run on every build catch regressions immediately rather than at the end of a sprint.
The comparison table between regression testing and retesting is worth understanding clearly: retesting confirms a specific bug is fixed; regression testing confirms nothing else broke as a result of fixing it.
