How to Do Regression Testing
To do regression testing, maintain a suite of checks that confirm existing features still work after each change. Select which cases to run by risk and impact, automate the stable high-value ones, and trigger the suite automatically on every build. Prioritize areas touched by the change plus critical end-to-end flows, and triage failures fast.
What is regression testing and when do you run it?
Regression testing verifies that recent changes, new features, bug fixes, configuration updates, did not break behaviour that previously worked. Software is interconnected, so a fix in one module can introduce a defect in another; regression testing is the safety net that catches those side effects before users do.
Run it whenever code changes: on every pull request, before every release, and after any production hotfix. The more frequently you run it, the smaller the change set behind each failure, which makes failures faster to diagnose.
How do you select what to retest?
You rarely need to rerun everything. Use a risk-based selection: always cover the modules touched by the change and their direct dependencies, plus the critical business flows (checkout, login, payment) regardless of what changed. This focuses effort where breakage is most likely and most costly.
Maintain a tiered suite, a fast smoke set for every commit, a broader regression set for pull requests, and a full suite before major releases. Tiering keeps everyday feedback fast while still giving thorough coverage at the moments that matter.
Which regression tests should you automate?
Automate the stable, repetitive, high-value cases, exactly the checks you would otherwise repeat by hand every release. Automated regression suites are the highest-ROI automation because the same cases run again and again across the product's life.
Hold off automating features that are still changing rapidly; the maintenance cost outweighs the benefit until behaviour settles. Keep exploratory and visual judgment checks manual. Promote a case into the automated suite once it has stabilized and proven worth re-running.
How do you keep the regression suite fast and trustworthy?
A slow or flaky suite gets ignored, which defeats its purpose. Keep it fast by parallelizing across workers and pushing logic down the test pyramid, favour fast API and unit-level checks over slow end-to-end UI tests wherever a lower layer can verify the same behaviour.
Keep it trustworthy by eliminating flakiness ruthlessly: deterministic waits, isolated data, and zero tolerance for tests that pass and fail at random. Triage every failure quickly into real bug, test bug, or environment issue so red builds always mean something.
How do teams sustain regression coverage as the product grows?
Regression suites need continuous curation, adding cases for new features, retiring obsolete ones, and keeping the suite green and fast. Appsierra's managed pods run regression testing as an ongoing discipline tied to each release, owning the quality outcome and keeping the safety net trustworthy, de-risked by Appsierra's own evaluation platform.
Frequently asked questions
What is the difference between regression testing and retesting?
Retesting confirms a specific defect was fixed by re-running the failing case. Regression testing confirms that the fix (or any other change) did not break previously working functionality elsewhere. Both are needed after a bug fix.
How often should regression tests run?
As often as code changes. Run a fast smoke subset on every commit, a broader suite on pull requests, and the full suite before releases. Frequent runs keep each failure tied to a small change set.
Do I have to rerun every test for every change?
No. Use risk-based selection: cover the changed modules and their dependencies plus critical end-to-end flows. Full-suite runs are best reserved for major releases; tiered suites keep everyday feedback fast.
How do I stop the regression suite from getting too slow?
Parallelize across workers, push checks down the test pyramid to faster API and unit layers, and remove redundant cases. A suite that takes hours gets skipped, so guard its runtime as a first-class concern.
Can regression testing be fully automated?
The stable, repetitive parts should be, since they run every release. Keep exploratory and visual-judgment checks manual. The right mix is mostly automated regression with targeted manual exploration around new or risky areas.
Want this done for you?
Appsierra's managed pods pick the right tools and practices, then own the testing outcome — de-risked by our own evaluation platform. Start with a low-risk pilot.