Buttons must do exactly what they say
I test the full path: open, enter data, validate, save, edit, cancel, delete, refresh, and repeat on a small screen. Empty controls and one-time success are not acceptable.
Failure behavior is part of the feature
Network timeouts, duplicate submissions, invalid files, and stale records need clear outcomes. The app should preserve work, explain the next step, and avoid creating duplicate data.
Release work stays visible
Every production pass includes syntax checks, automated tests, browser console review, responsive screenshots, and manual workflow checks. Remaining limits belong in release notes instead of being hidden behind a green status.