Is it possible to quickly create/restore database snapshots with PostgreSQL?
You could use file-system level snapshots, but that is often pretty cumbersome, needs special file systems, and is not always available, especially on aging laptops. ;-)

How about you create your base state as a database, and then create a new database from it for your test run, using the CREATE DATABASE ... TEMPLATE functionality.  After the test, you throw that database away.  Then your speed constraint is essentially only the time to cp -R the database directory.  That's about as fast as you're going to get without file system snapshot magic.