UL testing has specific requirements and testing methods, so Design1 the engineering company would design and test their unit accordingly prior to submitting for the test. Normally, UL would recommend the manufacturer to start the application process even during the developments, so the UL would be able to suggest the area of improvements.
Having said all these, I believe WDRP may already initiate the communication with UL office to see the requirements and what it takes to comply. Thus, IMHO the UL testing would be a smooth ride for them.