JUnit.org Resources for Test Driven Development

Hello,
I want to write tests for component written in Java an C / C++ (using JNI).
Software is working on WIN, LINUX and QNX on different hardware platforms.
What technique would you recommend to write tests?
Currently I have some simple unit tests for pure Java logic.
Is it possible to use junit for testing JNI parts (Java and C++)?

Thanks for help
Dominik