So you could probably surround your tests in transactions which is a typical approach for testing with ActiveRecord
in Ruby. That might be more performant, but it should also help keep the database clean.
But you're right, the impermanent database is the tool that's provided in Neo4j for temporary databases for testing. I think that's only available if you're running JRuby, though. I did run across this, though:
https://groups.google.com/forum/#!topic/neo4j/7xeEPWEiqD0
Which links to a project which lets you start up a Neo4j server in "in memory" mode (using the impermanent database):
https://github.com/jexp/neo4j-in-memory-server
That's showing examples for Neo4j 2.0.0, so I don't know if it would work for later versions, but it might be worth a shot for your testing database.
EDIT: Another thing that I just thought of is to use the vcr
gem:
https://github.com/vcr/vcr
It basically records all of the requests made to your server and then plays them back. This works great for API endpoints where result are idempotent, but if you use it for a database like Neo4j you should make sure that your tests are clearing the database before every test run so that it always starts fresh