I have several dozen tests that run in completely separate DBs. With SQLite, the test suite runs through in 1 second:

  $ time go test github.com/sapcc/limes/... | grep -v 'no test files'
  ok      github.com/sapcc/limes  0.004s
  ok      github.com/sapcc/limes/pkg/api  0.515s
  ok      github.com/sapcc/limes/pkg/collector    0.449s
  ok      github.com/sapcc/limes/pkg/core 0.006s

I doubt that you can setup and tear down several dozen Postgreses in that time.