I've done "write a script to reset the database" before, although not for Pgsql. The effort and potential snags involved make it nowhere near as trivial as docker rm && docker run.

There are also other scenarios that become really simple with disposable DB instances. Want to test a remote data transfer feature? Just spin up two databases.

Drop-create scripts! One of my first epiphanies in the testing world.

Create only scripts can also be great in the right context.

Namely a context like travis-ci where you get a new clean environment each time.

Personally, I've develop few libraries/web UIs that relies on external software like a DNS server or an ldap directory.

And for those, I've a quick and dirty shell script that deploys bind/OpenLDAP.

It's far easier, faster and more accurate than mocking.

For example, what comes to my mind is the testing I do for all the SSL/TLS modes I support (SSL, StartTLS, certificate check disable or not, etc) in my ldap web application.

Travis also has available services in their build envs (stuff like redis, mongodb, mysql, cassandra...).

I do this with rsync to restore a snapshot of the database data folder.