private static void dropBallsToSystem(int depth, int ballCount, ISystemService systemService, IBallService ballService) { var system = systemService.CreateSystem(depth); for (var i = 0; i < ballCount; i++) { var ball = ballService.CreateBall(i); systemService.AddBallToSystem(ball, system); } var emptyContainers = systemService.GetEmptyContainers(system); Console.WriteLine("Empty Container Names:" + string.Join(",", emptyContainers.Select(p => p.Name).ToArray())); }