Agree with this.
When they tested our birds, we had nine and they only needed to test three, but it could be different depending on what state you live in. I would call your counties 4-H extension office, they will probably know of someone.
The guy who tests my birds, who is probably the best and only person available in North/Central New Jersey, only requires a couple to be tested. That way they can say they originate from a pullorum free flock. None of the birds I take to shows were actually tested themselves, they just have the cert from other birds in the flock being tested, so I can say they originate from a pullorum free flock.