regression testing
termprogrammingops culture
Re-running existing tests to confirm that a change did not break something that already worked.
The name is the point: a regression is progress running backwards, and the whole reason a suite accumulates is that every bug fixed once should stay fixed. Mature teams add a test reproducing each bug at the moment they fix it, so the suite becomes a memory of everything that ever went wrong. Skipping it under deadline pressure is the classic false economy behind the emergency hotfix a week later.
Also known as: regression suite, regression test