Interesting topic, I had genetic testing after cancer diagnosis when still on private insurance. May not been same as your asking about. I am now on Medicare and did search for rules. Here is Medicare document with rules for coverage:

Of course, would try to verify with billing dept before any testing. Mayo does have a dept in billing that does estimates, I tried to get an estimate for a different non-covered appointment / test and provider actually had to ordered first, then billing could provide me an estimate. Once found out cost, I cancelled the appointment / test.

Good luck., Laurie