There is a race condition in tests run by prove from Test::Harness.
Run the following command two times in a row:
prove -l t/tests.t :: --tests 'User::Edit'
The second time, both tests should fail with:
Catalyst error screen: Caught exception in MusicBrainz::Server::View::Default->process "Couldn't connect to the renderer. at /musicbrainz-server/lib/MusicBrainz/Server/View/Base.pm line 36."
Delete socket file /tmp/musicbrainz-server.socket.