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.
Use Stellar, it's like git for databases:
Stellar allows you to quickly restore database when you are e.g. writing database migrations, switching branches or messing with SQL. PostgreSQL and MySQL (partially) are supported.
If your database runs in Virtualbox, you can easily save snapshots and restore snapshots of both the database state and the OS itself in a few seconds (or 1-2 minutes if you really have a lot of data in the database or the OS or very little memory allocated to the virtual machine) for free.
In your/most cases, it would be best to install a lightweight linux (than a Windows server) for running the virtual machine where the database is hosted given you mention you have little ressources available on your laptop.
On the production site, I use MediaTemple's snapshot backups to achieve the same result (but it's 20$ per backup slot and specific to that webhosting service, so that may not fit you).