Usually the FCC testing will test that the receiver does not respond inappropriately to signals outside its designated band. However the real focus of the testing is the transmitter, as receivers don't usually mess up your neighbour's baby monitor.
You can get some absolutely magic software-defined radios that can receive pretty much anything under the sun. (Hey, they will also pick up radio waves from the sun, but it doesn't have much to say at those frequencies.) They're sold as "USB TV receivers". But with the right software you can tune them to any frequency and see what your transmitter is saying. Decoding the serial protocol it uses will be the hardest part.