What application process are you looking at: DYS, a GT program, something else? Also, how old is your child and do you suspect that he is HG/EG/PG or 2e at all?

The further out of the typical he is likely to be and if you suspect any disabilities, the more I'd be concerned about dealing with a tester who is familiar with HG kids. You could start by contacting any local gifted schools (if you have any) to see if they have any recommended testers.