What to check, and how much.
THE MINIMUM FOR ANY CHANGE
The page or feature you changed The homepage One other page, to confirm nothing global broke The admin area Any form
FOR A SHOP, ALSO
Add to cart Complete a checkout with a real payment method Confirm order emails arrive
Checkout is the thing most worth testing and most often skipped.
AUTOMATED TESTS
Worth having for anything with real complexity. Even a small suite covering critical paths catches regressions that manual testing misses.
Run them before deployment, not after.
ON STAGING
Test the actual deployment procedure, not just the code. A deployment that works on your machine and fails on the server is a common surprise.
AFTER DEPLOYING
Repeat the minimum checks on production immediately. Do not deploy and walk away.
WHAT PEOPLE SKIP
Testing on a phone. Most visitors are on one, and layout and interaction problems frequently appear only there.
