JUnit test cases for Windchill functionalities

Hello,

I wanted to write JUnit test cases for Windchill customizations, I am not able to find a guide document for the same, can any of you shed some light on how one can start writing test cases for Windchill code ?. I am able to write the test cases for basic functionality like fetching an attribute but not for complex scenarios.

Requesting your help with the same.

Thanks,

Hari