Well it's fairly simple to tell whose turn it is. Most of the time each players 'turn' is started movement of troops (or arrowfire).

If you watch a battle and someone advances (or their sprite changes to the 'attack' sprite) it's their turn. How you tell if repel works, is by checking the hit points of the units in the front line before they attack then after they attack. The ones who have been damaged have been repelled (unless there is an effect, like Fire Shield, etc on them).

While incredibly cumbersome with the current battle playback system (no VCR controls) it's possible to test repels and other things by staging battles if you have alot of paitence. Or alternatively if you arn't looking for something new, try the combat simulator.