pgtestdb should work for your use case, and because each test gets its own database, you shouldn't run into any conflicts that are caused by different tests each trying to write data with the same ID. If it doesn't, please let me know and/or file a bug in Github.
One other nice thing about pgtestdb is that you can run all your tests in parallel, and if a test fails the related db will be left up for you to connect to via psql (helps a lot with debugging.) Compared to your transaction setup, the only data in the db will be from the test that failed.
Comments
pgtestdb should work for your use case, and because each test gets its own database, you shouldn't run into any conflicts that are caused by different tests each trying to write data with the same ID. If it doesn't, please let me know and/or file a bug in Github.
One other nice thing about pgtestdb is that you can run all your tests in parallel, and if a test fails the related db will be left up for you to connect to via psql (helps a lot with debugging.) Compared to your transaction setup, the only data in the db will be from the test that failed.