SoapUI uses XPath to manipulate XML. But we cannot use XPath expressions on JSON.
But soapUI have capability to convert JSON to XML.
Only difference is that instead of using Response property you have to use ResponseAsXml property.
ResponseAsXml in soapUI will convert JSON to XML.
The best and easy way to assert on a JSON response is to use a Groovy Script Assertion
Now lets see how to use Script Assertion on a JSON reponse.
"Token": { "UserId": "test@test.com", "TimeStamp": "31/12/2014", "SignedInAs": "test" },
The following is the script we can use to assert the content of the above Json response
import groovy.json.JsonSlurper def response = messageExchange.response.responseContent def slurper = new JsonSlurper() def json = slurper.parseText response assert json.Token.UserId = "test@test.com" assert json.Token.TimeStamp == "31/12/2014" assert json.Token.SignedInAs == "test"