Since the self-detonating photon is processed internally to the player's session, and doesn't involve any events between players, there isn't much that could go wrong with it. I'd expect a test game to be the same as a live game. Either you hit something that triggers your photon or you don't. And if the player is saying that no output suggested that the photon went off, then clearly the game isn't triggering the photon (as opposed to a case where it triggers, but the event got lots somewhere). If anything happens that would trigger a photon, and the player has at least one photon, there would be a message saying that it went off, whether or not there was any effect of the detonation.