I haven't had a chance to try it yet, but IntegreSQL[0] looks like this on steroids. It allows you to create a template (run migrations and seed data), and then uses Postgres's built in cloning functionality to maintain a pool of fresh databases. They claim 500ms to clone a database without the pool, and that the pool pretty much hides the latency entirely.
[0]: https://github.com/allaboutapps/integresql