There is no way to play the route (if you mean driving simulation) inside S&T itself. I don't know what is the purpose of doing that?
One thing i have already tried is to use Franson gpsgate which has a gps simulation mode. But it would not simulate your route, but a list of moving from say gps coordinate to another. One time i have enter for testing a big list of coordinates around my route. But S&T may go off route because between simulated coordinates, it is like a "straight line" and not necessary following a curve like a real route could be. So in simulation, you may get "off-route" message often between the pts.
But just for testing without a gps, it could help to see how things go. I think franson gpsgate has a free 30 days trial:
GPS splitter, simulator and logger. Serial port splitter. - Franson GpsGate
But Larry proposal to step along route segments manually could be a compromise...