I wrote the new tests in the canonical way but I still had the problem of all those seconds spent seeding the db even when I run a single test. I wrote a couple of scripts that dumped the db at the end of the tests (if a dump did not exist yet) and reloaded it at the beginning of the tests. This is much faster. I still have to clear the test db and reseed it when I switch branch, because I don't have a dump list branch.
Maybe I can create a template with the data in it. Or finally rewrite every single old test.