Simulating gps movement on real iOS device

I've seen a few questions on this but none explain how to do my specific scenario:

I need to test my app works for tracking a user's location over long distances. I'm using a 3rd party to test it, so I need a way for them to simulate like they are actually moving without really moving at all or leaving their home. I was hoping to do this using a GPX or KML file that I have pre-recorded for a few routes to simulate. I really want it to be some script or app that "replays" the GPX or KML lat/long sequence on the physical device but is not actually part of my app so I can be sure app is unaware that the data is fake. I've seen apps in the App Store that let you change to a single point on a map, but I really want something that will let me replay a sequence.