ABAP Unit Test Classes - Good References

There is some documentation in sap.com.

Also, there is a German PDF (see here) that may be helpful if you know some German ;-) At least it contains a few email addresses of people that may be able to help. Not sure because the PDF is from a conference in 2003, so the contact info may not be too up to date.

Lastly. there seems to be a German book (on Amazon Germany) .. again not sure if that helps you.