@Test
 public void ball_starts_rolling_when_all_players_signal_done() throws Exception {
   // arrange
   Player p2 = new Player();
   Player p3 = new Player();
   rt.placeBet(p, Field.forNumber(1), 10);
   rt.placeBet(p2, Field.forNumber(2), 10);
   rt.placeBet(p3, Field.forNumber(3), 10);
   // act
   rt.done(p);
   rt.done(p2);
   rt.done(p3);
   assertTrue(rt.isBallRolling());
 }