Add comprehensive test suite for game mechanics and level handling

- Introduced `test_final_level_flow.py` to validate final level transitions and game end scenarios.
- Created `test_game_over_flow.py` to ensure game over conditions trigger correctly based on rat counts.
- Implemented `test_keybindings.py` to verify keybinding configurations and their context-specific actions.
- Developed `test_level_editor.py` to assess level editor functionalities and layout computations.
- Added `test_level_io.py` for testing level data serialization and deserialization.
- Established `test_loop_logic_parity.py` to ensure consistent game state across multiple simulation runs.
- Created `test_non_regression.py` to simulate game behavior and capture states for future verification.
- Implemented `test_verify.py` to compare current game states against a golden master for regression detection.

engine/unit_manager.py

@@ -4,6 +4,8 @@ from units import gas, rat, bomb, mine
 
 
 
+from units.unit import UnitType
+
 class UnitManager:
     def __init__(self, game):
         self.game = game
@@ -24,11 +26,10 @@ class UnitManager:
 
     def has_weapon_at(self, position):
         """Check if there's a weapon (bomb, gas, mine) at the given position"""
+        weapon_types = {UnitType.BOMB_TIMER, UnitType.BOMB_NUCLEAR, UnitType.GAS, UnitType.MINE}
         for unit in self.game.units.values():
-            if unit.position == position:
-                # Check if it's a weapon type (not a rat or points)
-                if isinstance(unit, (bomb.Timer, bomb.NuclearBomb, gas.Gas, mine.Mine)):
-                    return True
+            if unit.position == position and unit.type in weapon_types:
+                return True
         return False
 
     def can_place_weapon_at(self, position):
@@ -43,11 +44,26 @@ class UnitManager:
         
     def count_rats(self):
         count = 0
+        rat_types = {UnitType.RAT_MALE, UnitType.RAT_FEMALE}
         for unit in self.game.units.values():
-            if isinstance(unit, rat.Rat):
+            if unit.type in rat_types:
                 count += 1
         return count
 
+    def refill_ammo(self):
+        """Randomly refill ammo during gameplay."""
+        import random
+        for ammo_type, data in self.game.ammo.items():
+            if ammo_type == "bomb":
+                if random.random() < 0.02:
+                    data["count"] = min(data["count"] + 1, data["max"])
+            elif ammo_type == "mine":
+                if random.random() < 0.05:
+                    data["count"] = min(data["count"] + 1, data["max"])
+            elif ammo_type == "gas":
+                if random.random() < 0.01:
+                    data["count"] = min(data["count"] + 1, data["max"])
+
     def spawn_gas(self, parent_id=None):
         if not self.can_place_weapon_at(self.game.pointer):
             return