I'm not aware of any tool, but a simple way to test is to edit and publish one content in one box and see if the changes were replicated in the other box
A testing tool could be practical if you want to test without having a site up and running. I've seen (and used) various tools for this purpose.
Found this old and archived repo now, that I havn't tested:
Is there a tool avalable to easily test that event replication between two EPiServer 11.x "boxes" function like it should?
I.e. to check that e.g. no firewalls etc. are blocking communication.