How to verify API responses in Katalon Studio

This is a companion discussion topic for the original entry at

How would I check for the existence of an element in a JSON response – but not care about the value…?

I do

import groovy.json.JsonSlurper as JsonSlurper
def jsonSlurper = new JsonSlurper()
def json = jsonSlurper.parseText(response.getResponseBodyContent())
WS.verifyNotEqual(json.field, null)

Maybe there is shorter, but this construction works for a lot of other situations too