SoapUI will probably always be one of my favorite development and testing tools. Recently I had the opportunity to explore its web service simulation and mocking capabilities.
I needed to create some fairly-detailed mock responses for a service where pretty much every element in schema for the response was optional. By default, soapUI does not add optional elements to the mock response XML. This was causing me a significant amount of pain. I noticed in the Preferences, WSDL Settings, that there was an "Include Optional" option that says "always include optional schema elements when creating requests":
I discovered that this option not only applies to creating requests, but also to creating mock responses. Problem solved. But I couldn't find this documented anywhere, so I wanted to point it out.