Regression Test

A regression test is a test that re-executes existing test cases after a code change to verify that previously working functionality has not been broken by the modification.

Regression tests guard against unintended side effects whenever a codebase changes — whether the change is a bug fix, a new feature, a dependency upgrade, or a configuration update. Because even small edits can silently break unrelated parts of a system, teams maintain a curated regression test suite that can be re-run quickly and reliably after each build.

In practice, regression testing sits inside the CI/CD pipeline, triggered automatically on every commit or pull request. The suite is rarely exhaustive; change impact analysis and test case prioritization help teams decide which areas carry the highest risk and deserve the most coverage in a given cycle. A lighter smoke test subset often runs first, with a full regression cycle reserved for release candidates or nightly builds.

Regression tests span multiple levels — unit, integration, and end-to-end — and are closely related to defect retest, which confirms a specific fix works, whereas regression testing confirms the fix did not break anything else. Over time, suites grow and require active maintenance: obsolete cases are retired, new scenarios are added, and test data management keeps the environment stable enough for results to be trustworthy.

Also known as: regression suite

• en.wikipedia.org — Regression testing