The SIP School™ has partnered with tekVizion to provide a virtual experience on SIP trunk configuration and operation within a Microsoft Skype for Business environment. This environment is available via their service called onTAP™.
The onTAP™ service provides virtual environments for a number of manufacturers and you can check out the details here http://www.tekvizion.com/services/ontap/
SIP trunk configuration is taught in The SIP School's SSCA® SIP training program yet with so many Phone System manufacturers and so many SIP trunk service providers around the world, there can be many cases of inconsistencies in the implementation of the SIP standards. Of course, as a manufacturer you can test out all service providers with your own system or you can work with tekVizion to do it for you.
"Many vendors have found that working with tekVizion can significantly reduce the costs and time it takes to verify interoperability across a multitude of providers." Tracy Venters, tekVizion.
Details of tekVizion's SIP trunk testing services can be found here