Regression testing

What is regression testing?

Regression testing re-runs existing tests after a code change to confirm that nothing which used to work is now broken. The name comes from regression itself: a defect that was fixed coming back, or a working feature breaking for no obvious reason. Every change risks it, whether the change is a bug fix, a new feature, or a refactor.

The risk is side effects. You patch one module and a function three layers away starts returning the wrong value. Regression testing is how teams catch that before it reaches production. A login that worked last week suddenly fails after an unrelated change to the session layer is exactly the kind of thing it surfaces. Done by hand it's slow and easy to skip, which is why regression testing earns its keep when it's automated and wired into a CI/CD pipeline, giving fast feedback the moment a change breaks something.

Scope is a real decision. Full regression runs the entire suite and gives the most coverage for the most time. Selective regression targets only the areas a given change is likely to touch, trading some coverage for speed while protecting the highest-risk paths. Most mature teams run both, depending on the change.

Regression testing at Dallonses

We treat regression suites as part of the codebase, not an afterthought. Tests run automatically in CI on every change, so a broken feature shows up in minutes rather than in a user's bug report. When a defect does slip through, the fix comes with a test that locks the behaviour down for good.

Global brands hand us products with years of accumulated logic that can't quietly break. Our quality assurance work maps the highest-risk paths first, automates them, and grows coverage as the product grows. The result is a team that ships changes without holding its breath, because the safety net is real and it runs every time.

Changing a system that can't afford silent breakage? Let's build the safety net that catches it.

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