How to I test my ISAAC nodes

What is the praxis of unit-testing, function-testing, system-testing nodes, gems, etc? Should I create mock-nodes and mock the tx’s and rx’s into a node I want to test?

Yes, a good approach to component/codelet testing would be to create test/mock codelets within gtest (make sure you register them) in your tests, setup an Application with your mock codelets connected to feed and receive messages to the codelet you want to test, run the application for some time until some node has success or time has elapsed, and then verify the collected results.