We haven't had our piano† tuned in a a few years (since before the pandemic began), and I have a tuning scheduled soon.
One thing I have wondered about when having the piano tuned in the past is how to check the piano technician's work relatively quickly before I pay them and send them on their way. I have hired the same company we have used before but it won't be the same technician. I don't expect they'll be "cheating" outright, but I know everyone makes mistakes and oversights.
I'm capable of tuning myself‡ so I know how to thoroughly check, but it seems unkind to spend a great deal of time exhaustively verifying the entire job.
So: I usually play a chromatic scale across the keyboard to check the unisons and just play around a little bit, in different octaves, and in distant keys with a mixture of close and wide voicing, etc.
Are there other things that could serve as a more effective "acceptance test" to catch common errors or omissions? Should I check each octave? Each fifth, to see that beat frequency gradually increases?
† The piano is an 18-year old Schimmel 120i Upright in daily casual use, bought new and generally well maintained. (Action reconditioned and regulated in 2014.) We are located near Chicago, and that means frequent, wide outdoor temperature & humidity variations occur. However, the piano is and always has been in a conditioned space with central humidification used during heating season. Since the last tuning, the piano has been moved (about 15'/5m horizontally) to a different room in the house. (It used to be against an exterior wall, but now is in the middle of a room.)
‡ Although this particular piano has always been tuned and serviced by professionals, I taught myself to tune by ear (with proper tools and a tuning fork pitch reference) as a university engineering student (late 1980s) because the ones in the student practice rooms were not well maintained. I also regularly tuned my prior piano (a P.A. Starck spinet, inherited in 1993 from my grandmother that my father and aunts had learned on in their childhood.)