The correct answer is Regression testing.

Regression testing is the process of retesting previously working functionality after changes such as patches or updates to ensure that no existing features have been broken. It commonly involves rerunning a suite of tests across multiple released builds or versions to verify stability and to uncover unintended side effects introduced by the change.

Fuzz testing is not correct because it supplies random or malformed inputs to software to uncover crashes and memory errors rather than systematically retesting existing functionality across builds.

Penetration testing is not correct because it simulates attacks to find security vulnerabilities and weaknesses rather than focusing on verifying that prior features still work after a patch.

Canary testing is not correct because it refers to rolling out a new build to a small subset of users to observe behavior in production rather than explicitly retesting multiple released builds to confirm previously working functionality.

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