Also, "jamming" can include sending distorted signals. These distortions can be a spoofed or malformed packet of data. Knowing what happens when a navigation tool suddenly thinks the vehicle is on the other side of the world is important. As is, ensuring that a garbage signal won't crash it.

Or less extreme things. Do the soldiers notice when their GPS shows them as half a mile away from where they need to be. In a slowly changing offset.