How to write testable code

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6. . public class Fight { private State state = new State(); private Player player1, player2; public Fight(Player player1, Player player2) { this.player1 = player1; this.player2 = player2; } ... public void attack(Player attacker, Weapon weapon) { Player opponent = getOpponentOf(attacker); int damage = calculateDamage(opponent, weapon); opponent.setHp(opponent.getHp() - damage); Utility.updatePlayer(opponent); updateState(); } public State getState() { return state; } ... }
7. . public class FightTest { @Test public void testAttack() { Player player1 = new Player(); Player player2 = new Player(); Weapon weapon = new Weapon(); Fight fight = new Fight(player1, player2); fight.attack(player1, weapon); fight.attack(player1, weapon); fight.attack(player1, weapon); State state = fight.getState(); assertThat(state.isFinished(), is(true)); } }
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9. public class Fight { private State state = new State(); private Player player1, player2; public Fight(Player player1, Player player2) { this.player1 = player1; this.player2 = player2; } ... public void attack(Player attacker, Weapon weapon) { Player opponent = getOpponentOf(attacker); int damage = calculateDamage(opponent, weapon); opponent.setHp(opponent.getHp() - damage); Utility.updatePlayer(opponent); updateState(); } public State getState() { return state; } ... } .
10. B . D public class Fight { private State state = new State(); private Player player1, player2; public Fight(Player player1, Player player2) { this.player1 = player1; this.player2 = player2; } ... public void attack(Player attacker, Weapon weapon) { Player opponent = getOpponentOf(attacker); int damage = calculateDamage(opponent, weapon); opponent.setHp(opponent.getHp() - damage); Utility.updatePlayer(opponent); updateState(); } public State getState() { return state; } ... } .
11. public class Fight { private State state = new State(); private Player player1, player2; public Fight(Player player1, Player player2) { this.player1 = player1; this.player2 = player2; } ... public void attack(Player attacker, Weapon weapon) { Player opponent = getOpponentOf(attacker); int damage = calculateDamage(opponent, weapon); opponent.setHp(opponent.getHp() - damage); Utility.updatePlayer(opponent); updateState(); } public State getState() { return state; } ... } .
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16. F . interface PlayerUpdater { public void updatePlayer(Player player); } F
17. public class PlayerUpdaterImpl implements PlayerUpdater { @Override public void updatePlayer(Player player) { Utility.updatePlayer(player); } } .
18. B . public class Fight { private State state = new State(); private Player player1, player2; private final PlayerUpdater updater; public Fight(Player player1, Player player2) { this(player1, player2, new PlayerUpdaterImpl()); } protected Fight(Player player1, Player player2, PlayerUpdater updater) { this.player1 = player1; this.player2 = player2; this.updater = updater; } ... public void attack(Player attacker, Weapon weapon) { Player opponent = getOpponentOf(attacker); int damage = calculateDamage(opponent, weapon); opponent.setHealth(opponent.getHealth() - damage); updater.updatePlayer(opponent); updateState(); } } . P U . . .. . F
19. P . ( ( public class Fight { private State state = new State(); private Player player1, player2; private final PlayerUpdater updater; public Fight(Player player1, Player player2) { this(player1, player2, new PlayerUpdaterImpl()); } protected Fight(Player player1, Player player2, PlayerUpdater updater) { this.player1 = player1; this.player2 = player2; this.updater = updater; } ... public void attack(Player attacker, Weapon weapon) { Player opponent = getOpponentOf(attacker); int damage = calculateDamage(opponent, weapon); opponent.setHealth(opponent.getHealth() - damage); updater.updatePlayer(opponent); updateState(); } } ) ) . I U B D ( I ( ( I F
20. import static org.mockito.Mockito.*; public class FightTest { @Test public void testAttack() { Player player1 = new Player(); Player player2 = new Player(); Weapon weapon = new Weapon(); // PlayerUpdater    PlayerUpdater updater = mock(PlayerUpdater.class); // Fight   Fight fight = new Fight(player1, player2, updater); fight.registerHit(player1, weapon); fight.registerHit(player1, weapon); fight.registerHit(player1, weapon); State state = fight.getState(); assertThat(state.isFinished(), is(true)); // updatePlayer() 3 
      verify(updater, times(3)).updatePlayer(player2); } } M . F P U F
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