noun
Software testing term: re-running tests to ensure that new changes haven't broken existing functionality.
新しい機能を追加した後、退行テストを実施した。
After adding the new feature, we ran regression tests.
Synonym also used in software engineering; 退行テスト is more common in some contexts, but both refer to regression testing.
Compound of 退行 (regression) and テスト (test), a direct calque from English 'regression test'.