7_Observer

Observer Coding Exercise

Imagine a game where one or more rats can attack a player. Each individual rat has an initial attack value of 1. However, rats attack as a swarm, so each rat's attack value is actually equal to the total number of rats in play.

Given that a rat enters play through the initializer and leaves play (dies) via its __exit__ method, please implement the Game and Rat classes so that, at any point in the game, the Attack value of a rat is always consistent.

Here's a sample unit test your code should pass:

def test_three_rats_one_dies(self):
    game = Game()
 
    rat = Rat(game)
    self.assertEqual(1, rat.attack)
 
    rat2 = Rat(game)
    self.assertEqual(2, rat.attack)
    self.assertEqual(2, rat2.attack)
 
    with Rat(game) as rat3:
        self.assertEqual(3, rat.attack)
        self.assertEqual(3, rat2.attack)
        self.assertEqual(3, rat3.attack)
 
    self.assertEqual(2, rat.attack)
    self.assertEqual(2, rat2.attack)