Where to find them: You may find them on the “Browser” page. They remain separate SVN repositories. (We’re using Trac’s multiple repository support.)
How to reference commits in tickets: Rather than [UT123] to reference a unit test changeset, you can use [123/tests]. Same goes for [D11] and [11/design]. Note though that the old ways still work (it’ll just redirect three times to get there).
Or, even better:¬ If a commit references a Trac ticket, it will now automatically be posted there, just like core commits.
Commit notifications: All three repositories send their commits to the wp-svn mailing list.
Where to post patches and create tickets: On core Trac. Items meant to be committed to the design repository were nearly always going to come from existing tickets anyway. If you happen to be proposing new unit tests for existing code, you may now just create a new ticket on core Trac. If you are proposing changes or improvements to the test framework itself, use the “Unit Tests” component. There are still some open tickets on on the old Trac, as well, but I’ve shut off ticket creation over there.
Why? This was an action item from the community summit. A number of developers felt it did not make sense to marginalize these projects on their own Trac installs. Now, you can follow them all in one place, and it ideally raises the profile of them too.