Testing the characteristics of switch modules is not always as simple as it seems. Some are easy because they have RF connectors, others use connectors not usually used for for RF applications, particularly those with bandwidths less than 100MHz
Some switch systems are designed to handle signals in 50 ohm transmission lines, others in 75 ohms.
Some modules are designed to handle differential signals using 2 pole switching, in this case the important parameter is the differential impedance. This is particularly true when handling signals like RS232 (and derivatives), telecomms signals and serial interfaces such as Ethernet and USB.
In a system of course it is possible that none of these conditions apply, but the only way that reproducible specification can be generated is by specifying a condition that can easily be checked. For the most part that means measuring in a single ended 50 ohm environment using either a ground pin on the user connector or the connector ground to terminate the coaxial connection screen.
Pickering have an informal guide to how to make practical RF measurements on RF characteristics of a module which may be helpful to users when verifying performance.