As far as I know there is no way of actually testing an antenna's capacity for function without specialized RF equipment.
Just hook it up and see how it does.
You can get inline amps for FM if you need more reach, but in my experience the OE antenna is pretty hard to beat unless amped for FM.
The problem with amps is it's not easy to find one that works well these days.
There is a lot of garbage out there, and if you do get one make sure you get one you can turn off separate of the radio.
A good strength signal can get garbled if over amplified, so being able to turn it off is a good thing.
