Testing JSON Rest Services

Hi,

I am trying to run a POST using the latest soapUI 4.0 beta 1.
I have setup the request and noticed the Media Type only contained - application/xml, text/xml and multipart-form data.
I noticed you can add media-types in the Representation tab so I entered the following:

Type=REQUEST
Media-Type=JSON
Status Codes=n/a
Q-Name=Left blank

In the Request window, I selected JSON from the Media Type and entered my JSON. I checked it was valid by using an online JSON validator.
When I try to execute this, I see errors in the XML tab and in the JSON tab, it says <Not JSON content>.

Can you let me know if its possible to use SOAP to test Posts that use JSON?
If so, how do I do it?

Thanks,
Cora