What Is Regression Testing?

Regression testing is the practice of re-running a set of previous tests after a code change to confirm that existing functionality, including analytics tags and data collection, still works correctly. In an analytics context, it means checking that a new page release didn't silently break a tag that was firing correctly before.

A checkout redesign can quietly break the Data Layer event a conversion tag depends on, with nobody noticing until reporting numbers look wrong weeks later. Regression testing catches that at the source, re-verifying known-good tag behavior every time code changes, ideally wired into a CI/CD Pipeline so it happens automatically rather than depending on someone remembering to check.