regression
Pronunciation: reh-GRESH-un
A bug or failure introduced into previously working software as an unintended consequence of a code change.
Full Definition
In software engineering, a regression is a defect that causes functionality that was previously working correctly to fail, typically after a code modification such as a new feature addition, a refactor, or a bug fix. The term is used in phrases such as 'regression bug', 'regression test', and 'regression suite'. A regression test is designed specifically to verify that prior functionality has not been broken. In editorial contexts, editors must be careful not to confuse 'regression' (a return to a worse state) with statistical regression, which is an entirely different concept from data science. 'Regression' in this context is always a negative outcome.
Usage
Usage note: In developer-tool contexts, 'regression' always refers to a reintroduced failure, not a statistical method. Use 'regression test' (not 'regress test') for the test type.
In Context
- "The hotfix introduced a regression in the login flow that had been stable for six months." — Bug report
- "The CI/CD pipeline runs a regression suite after every merge to catch unintended breakage." — Quality assurance documentation