Not breaking your live site.
BEFORE ANY CHANGE
Back up.
For a version change, that is not optional.
WHERE TO TEST
A staging copy, if you have one.
Or a subdomain with a copy of the site.
USING PER-DIRECTORY VERSIONS
Set the new version on a test directory containing a copy.
Test there before changing the live site.
WHAT TO TEST
Every page type Forms and notifications Login Checkout
Anything using an extension: images, encryption, external connections
CHECK THE ERROR LOG
Even when everything appears to work.
Warnings indicate future failures.
IF SOMETHING BREAKS
Revert immediately, then investigate.
A live site working on an old version is better than a broken site on a new one.
AFTER A SUCCESSFUL TEST
Apply to the live site during a quiet period, and test again.
