Creating Custom Assertion

Hi,

I am trying to create custom assertion in SoapUI 5. I went through the following links http://blog.smartbear.com/api-testing/c ... in-soapui/
http://www.soapui.org/Developers-Corner ... ories.html

I created a custom factory class which extends from AbstractTestAssertionFactory.I also created another class which extends WsdlMessageAssertion. Now when i package this into jar place it into ext folder, the factory classes are loaded properly in soapui. But, I am unable to see my custom assertion in the list of available assertions. Do i have to implement additional classes/interfaces to get this working?
Or is there any detailed tutorial available for creating custom assertion similar to custom test step tutorial mentioned above?

Thanks,
Neha