ERROR [WsdlTestCase] Failed to create test step for [DataSource]

Hi,

I'm trying to access my soapui project from the api and execute selected testcase.
the following line: wsdlProject = new WsdlProject([filename])
returns this message: "ERROR [WsdlTestCase] Failed to create test step for [DataSource]"

I understood this is soapui pro specific testcase that require soapui pro core initialization. I need your assistant on that.

Thanks,
Chen.