What is Regression Testing?
Regression testing re-runs tests on existing functionality after code changes to confirm that what worked before still works. The term refers to a regression - when a previously working feature unexpectedly breaks - and the testing exists to catch those breaks before users do.
How does regression testing work?
Regression testing re-executes a set of existing tests after any change to the code - a new feature, a bug fix, an update or a configuration change - to verify that previously working functionality has not broken. Software is deeply interconnected, so a change in one place can have unintended effects elsewhere, sometimes far from where the edit was made. Regression testing exists to catch those side effects. Teams maintain a suite of tests covering important behaviour and run it whenever the code changes, comparing results against the known-good baseline.
Because the suite is run repeatedly, regression testing is a prime candidate for automation. Automated regression tests run quickly and consistently, often on every code change, so a break is caught within minutes rather than discovered by a user weeks later.
Why regression testing matters
The most damaging defects are often not in the new feature but in something that used to work and quietly broke. These regressions are dangerous precisely because nobody is looking at that area. Regression testing matters because it provides a safety net that lets teams change software confidently - shipping new features and fixes without fear of silently undoing past work. Without it, every change carries hidden risk, and teams either slow down out of caution or ship breakages they only learn about from frustrated users.
When should you run regression tests?
Regression testing applies whenever code changes, particularly:
- After bug fixes - to confirm the fix did not break something else.
- After new features - to check existing behaviour still holds.
- Before a release - as a final safety check across the product.
- After dependency or configuration updates - which can have wide effects.
Regression testing best practices
Automate the regression suite so it can run frequently and consistently without huge manual effort, ideally on every change through a continuous integration pipeline. Keep the suite focused on important, stable behaviour rather than letting it sprawl into slow, brittle tests nobody trusts. Add a regression test whenever a bug is fixed, so the same defect can never silently return. And maintain the suite actively - remove tests that no longer reflect the product and update those that do, so it stays a trustworthy signal.
How PixelForce approaches regression testing
At PixelForce, regression testing is part of Phase 2 - Development, QA and Release and continues through Phase 3 - Post Launch Support, where our in-house Adelaide team protects a live product as it evolves. Every change is checked against existing behaviour rather than assumed safe, which is part of how we sustain 99.99% crash-free reliability across 100+ products shipped. Ongoing regression coverage is a core element of the app maintenance and support we provide, ensuring updates improve a product without quietly breaking what already works. Catching regressions before release, not after, is what lets a product keep changing safely.
Where this applies
The PixelForce services where Regression Testing matters most - explore how we put it to work in client products.
Related terms
Other glossary definitions closely related to Regression Testing.
Frequently asked questions
Retesting confirms that a specific defect which was reported has actually been fixed - it targets the exact thing that was broken. Regression testing is broader: it checks that the fix, or any other change, has not broken previously working functionality elsewhere in the product. In short, retesting verifies the fix; regression testing verifies that nothing else was harmed in the process. Both usually run together after a change.
Wherever practical, yes. Regression suites are run repeatedly on every change, which is exactly the kind of repetitive, stable work automation handles best - quickly, consistently and without fatigue. Automated regression tests can run on every code change, catching breaks within minutes. Some exploratory or visual checks still benefit from human judgement, but the core regression suite delivering the most value is almost always automated to keep it fast and reliable.
Whenever the code changes in a way that could affect existing behaviour - after bug fixes, after adding features, after updating dependencies or configuration, and as a final check before a release. With automation, many teams run regression tests on every change through a continuous integration pipeline, so problems surface immediately. The principle is simple: if something could have broken existing functionality, regression testing should confirm that it has not.
The name comes from the word regression, meaning a return to a worse state. In software, a regression is when a feature that previously worked unexpectedly breaks because of a code change. Regression testing is the practice of detecting these breaks - confirming the product has not regressed. The focus is not on testing new functionality but on protecting existing functionality from being silently undone by ongoing changes.
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