Regression Testing

A regression is when fixing one thing breaks another: the change works, and somewhere across the system, something that used to work stops. Regression testing is the defence — re-running the suite after every change to prove the old behaviour still holds. It is the least glamorous testing and the most economically important.

What It Is

Regression testing re-executes existing tests after every change to confirm that previously working functionality still works. Its economics are brutal without automation: a system with a thousand test cases cannot be manually re-verified on every release, so either the suite is automated (and runs in CI on every change) or regression checking shrinks to whatever a release team can manually re-touch — which is how systems rot one release at a time. Full regression suites run everything; risk-based approaches select suites by the area changed. The regression suite is also the institutional memory of every past defect: each fixed bug becomes a test that fails if it ever returns.

Why It Matters to You

For executives, regression automation is the single strongest predictor of whether a vendor or team can ship frequently without breaking things — the capability that makes weekly releases safe instead of terrifying. The questions that map it: is the regression suite automated, does it run on every change (not just before releases), and how long does it take (suites that take a day get skipped under pressure, which is when they matter most)? The pathology to watch is the reverse: teams that must manually regression-test before every release consequently release rarely, batch changes to make releases worth the ceremony, and then ship big risky releases — the death spiral of legacy delivery, entered through this one door.

When You'll Meet It

In engineering assessments and delivery reviews. Ask for the automated regression suite's coverage area and runtime — the answers predict release cadence better than any roadmap.