nonregression

Nonregression refers to practices in software development aimed at ensuring that changes to a system do not degrade existing behavior. The term is most often used in the context of nonregression testing, a form of regression testing that concentrates on preserving previously verified functionality.

Nonregression testing involves running a predefined suite of tests after code changes, configuration updates, or environment shifts. The goal is to detect defects or behavioral changes introduced by modifications. It is typically automated and integrated into continuous integration and continuous delivery pipelines, enabling frequent releases while maintaining quality. Test suites for nonregression often include functional tests that exercise user-facing features, but may also cover performance, security, and compatibility checks that were previously stable.

Strategies include selecting a stable baseline version, reusing existing regression tests, and applying impact analysis to focus on parts of the system most affected by changes. Teams must balance test coverage with maintenance cost, as failing or outdated tests can undermine confidence. Flaky tests must be identified and fixed to preserve reliability.

Benefits of nonregression testing include reduced risk of introducing regressions, support for rapid iteration and predictable quality, and documentation of preserved behavior. Limitations include incomplete coverage that may miss regressions, ongoing maintenance requirements for test suites, and the risk of overreliance on automated tests that can overlook user experience issues.

Relation to other concepts: nonregression is distinct from exploratory testing but complements it by providing repeatable checks against known behavior. In practice, it is a core aspect of quality assurance in modern software development.