See T402597: Exploratory testing on PHP 8.3 for MediaWiki Platform Team components for context. T384232: QA for SUL3 on testwikis has more info on some checklist items.

Signup

• basic user account creation ✅
• email notification gets sent, links use canonical domain ✅
• incorrect captcha prevents signup ✅
• title-blacklisted user cannot signup, gets reasonable error message (test both the JS validator on the username field, and the form submit) ✅
• singing up with IDN homograph equivalent of existing username prevented by AntiSpoof (test both the JS dropdown on the username field, and the form submit) ✅
• AbuseFilter can block account creation (you can make a test filter on testwiki with something like action == "createaccount" & accountname == "MyTestAccount") (test both the JS validator on the username field, and the form submit) ✅
• NewUserMessage welcome message (especially that it doesn't end up with auth.wikimedia.org URLs due to parser cache pollution) ✅

API

• create account action API ✅
• sign up on one of the WMF mobile apps (skipped ❌). See: T403824.

Temp users

• temp user creation via edit works in basic editor ✅
• temp user creation via edit works in some JS editor, e.g. DiscussionTools ✅
• temp user can use Special:CreateAccount to turn into a named user ✅