Do you use any transformers? What do you see if you enable a message tracing? Is the message content null on OUT phase? Showing of your switchyard.xml might help to find where is the problem.
It seems that your problem is with the stub created. Probably the address is not correct.
I would recommend you to:
- Verify the address where the WS is deployed. You can see it in the log files.
- Use Switchyard capabilities to invoke services with JUnit. You can see some examples in the quickstarts, or here: http://unpoucode.blogspot.co.uk/2014/03/junit-in-switchyard.html
- use soapui or any other client that avoid you the creation of the stub.
Hope it helps.
Keep in mind I'm not switchyard developer, so I might be wrong. Don't shoot me if I am, just trying to help.