src/main/java/Monster/MovementPatterns.java

@@ -14,8 +14,8 @@ public enum MovementPatterns {
         this.id = id;
     }
 
-    public Set<Position> findLegalDestinations(Position position) {
+    public List<Position> findLegalDestinations(Position position) {
-        Set<Position> legalDestinations = new HashSet<>();
+        List<Position> legalDestinations = new ArrayList<>();
         int x = position.x();
         int y = position.y();
 

src/main/java/Monster/Shade.java

@@ -17,7 +17,7 @@ public class Shade extends Monster implements CanMove, CanAttack {
     private List<Position> validDestinations = new ArrayList<>();
 
     public Shade() {
-        super(MAX_HEALTH, MAX_ENERGY, Monster.DEFAULT_POSITION);
+        super(MAX_HEALTH, MAX_ENERGY, DEFAULT_POSITION);
     }
 
     public Shade(int health, int energy, Position position) {
@@ -120,7 +120,7 @@ public class Shade extends Monster implements CanMove, CanAttack {
         validDestinations.clear();
         for (MovementPatterns move : MOVES) {
             if (move.cost <= energy) {
-                Set<Position> destinations = move.findLegalDestinations(position);
+                List<Position> destinations = move.findLegalDestinations(position);
                 for (Position destination : destinations) {
                     if (noPlayerIsAtPosition(destination, world)) {
                         validDestinations.add(destination);

src/main/java/Monster/Troll.java

@@ -1,8 +1,154 @@
 package Monster;
 
-public abstract class Troll extends Monster implements CanMove, CanAttack {
+import Entity.Entity;
+import Entity.Player;
+import Entity.Position;
+import World.World;
+
+import java.util.*;
+
+import static java.util.Objects.isNull;
+
+public class Troll extends Monster implements CanMove, CanAttack {
+    public static final List<Biomes> HABITAT = Collections.unmodifiableList(Arrays.asList(Biomes.FOREST, Biomes.MOUNTAIN));
+    public static final List<MovementPatterns> MOVES = Collections.unmodifiableList(Arrays.asList(MovementPatterns.ONE_DIAGONAL_STEP, MovementPatterns.TWO_STEPS_IN_STRAIGHT_LINE));
+    public static final int MAX_HEALTH = 80;
+    public static final int MAX_ENERGY = 100;
+
+    private static final int HEALTH_PER_HEAL = 6;
+    private static final int ENERGY_COST_PER_HEAL = 3;
+
+    private Random random = new Random();
+    private List<Position> validDestinations = new ArrayList<>();
 
     public Troll() {
-        super(0,0,Monster.DEFAULT_POSITION);
+        super(MAX_HEALTH, MAX_ENERGY, DEFAULT_POSITION);
+    }
+
+    public Troll(int health, int energy, Position position) {
+        super(health, energy, position);
+        enforceHealthValueBoundries();
+        enforceEnergyValueBoundries();
+    }
+
+    public boolean heal() {
+        if (isDead()) {
+            return false;
+        }
+        if (health == MIN_HEALTH) {
+            return false;
+        }
+        if (health == MAX_HEALTH) {
+            return false;
+        }
+        if (energy < ENERGY_COST_PER_HEAL) {
+            return false;
+        }
+
+        health += HEALTH_PER_HEAL;
+        energy -= ENERGY_COST_PER_HEAL;
+        enforceHealthValueBoundries();
+
+        return true;
+    }
+
+    public boolean takeDamage(int amount) {
+        if (amount < 0) {
+            return false;
+        }
+        if (health - amount <= 0) {
+            kill();
+            return true;
+        }
+        else {
+            health =- amount;
+            return true;
+        }
+    }
+
+    public boolean performAttack(Attacks attack, Player player) {
+        if (isDead()) {
+            return false;
+        }
+        if (attack.cost > energy) {
+            return false;
+        }
+
+        return true;
+    }
+
+    public boolean move(World world) {
+        if (isDead()) {
+            return false;
+        }
+        updateDestinations(position, world);
+        if (validDestinations.isEmpty()) {
+            return false;
+        }
+        position = validDestinations.get(random.nextInt(validDestinations.size()));
+        updateDestinations(position, world);
+        return true;
+    }
+
+    public boolean moveTo(Position destination, World world) {
+        if (isDead()) {
+            return false;
+        }
+        if (playerIsAtPosition(destination, world)) {
+            return false;
+        }
+
+        position = destination;
+        updateDestinations(position, world);
+        return true;
+    }
+
+    private void updateDestinations(Position position, World world) {
+        validDestinations.clear();
+        for (MovementPatterns move : MOVES) {
+            if (move.cost <= energy) {
+                List<Position> destinations = move.findLegalDestinations(position);
+                for (Position destination : destinations) {
+                    if (noPlayerIsAtPosition(destination, world)) {
+                        validDestinations.add(destination);
+                    }
+                }
+            }
+        }
+    }
+
+    private boolean playerIsAtPosition(Position position, World world) {
+        List<Entity> entitiesAtPosition = world.getPositionEntityMap().get(position);
+        if (isNull(entitiesAtPosition)) {
+            return false;
+        }
+        for (Entity entity : entitiesAtPosition) {
+            if (entity instanceof Player) {
+                return true;
+            }
+        }
+        return false;
+    }
+
+    private boolean noPlayerIsAtPosition(Position position, World world) {
+        return !playerIsAtPosition(position, world);
+    }
+
+    private void enforceHealthValueBoundries() {
+        if (health > MAX_HEALTH) {
+            health = MAX_HEALTH;
+        }
+        else if (health <= MIN_HEALTH) {
+            health = 1;
+        }
+    }
+
+    private void enforceEnergyValueBoundries() {
+        if (energy > MAX_ENERGY) {
+            energy = MAX_ENERGY;
+        }
+        else if (energy < MIN_ENERGY) {
+            energy = MIN_ENERGY;
+        }
     }
 }

src/test/java/MonsterTest.java

@@ -108,14 +108,17 @@ public class MonsterTest {
         assertThat(shade.performAttack(Attacks.CHILL, mockPlayer), equalTo(false));
     }
 
-    /*@Test
+    @Test
     void only_moves_within_energy_budget_are_performed() {
-        Troll troll = new Troll(Troll.MAX_HEALTH)
+        Troll troll = new Troll(Troll.MAX_HEALTH, 1, Troll.DEFAULT_POSITION);
-    }*/
+        List<Position> movesWithinBudget = MovementPatterns.ONE_DIAGONAL_STEP.findLegalDestinations(troll.getPosition());
+        troll.move(mockWorld);
+
+        assertThat(movesWithinBudget, hasItem(troll.getPosition()));
+    }
 
     @Test
     void use_of_attack_not_in_arsenal_is_rejected() {
-
     }