First off thanks. Now a few things:
Have you seen the testdwr project in subversion? It is a web based testing application that allows us to test both the server and the client. We have quite an extensive listing of test-cases and this is what I meant by adding a test case (not a standalone Junit test). I recommend you download the app and if possible add the test case there. Otherwise I can do it (let me know).
Secondly, I am happy you are helping out but before you do the work you should re-assign the issue (if you can) or just let me know you want to work on it and I will assign it to you. That way we don't duplicate work.
Lastly, regarding the changes to the Enum converter it appears the changes you have made affect the documentation (for the inbound conversion):
If no match is found in the given enum, then an exception will be thrown.
I am assuming a ConversionException was being thrown on the inbound side before (instead of null)? Is that correct?
The changes to the outbound side look good.