Is it possible to have this persist to a file?

[Wavesonics]

So we don't lose data on every start

[honourednihilist]

Why do you need it? It is better to start from a clean database for test purposes.

[Wavesonics]

My plan was to have a prepopulated database that everything could load.

[honourednihilist]

I'd propose to prepare SQL-scripts for this and run them before tests. You could use database migration tools (here is an example - https://github.com/honourednihilist/gradle-postgresql-embedded-example/blob/master/src/main/liquibase/db/changelog/db.changelog-0.1.0.xml). It will be a reusable piece of work. For example, if you migrate from this gradle plugin to something else.