Receive GPS Antenna and cable simple confirmation of operation
A TDR (Time Domain Reflectometer) would seem to be the answer here - we used these in the Navy to ring out long RF cable runs/transmission lines. It will tell you if there are any shorts or opens (and where they are) and whether the end is terminated in a proper load (antenna connected).

Its a relatively pricy piece of equipment at about $1500-$2000, but its a huge labor saver.