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.

tests/test_level_io.py

@@ -0,0 +1,75 @@
+#!/usr/bin/env python3
+
+import json
+import tempfile
+import unittest
+from pathlib import Path
+
+from engine import maze
+
+
+class LevelIoTests(unittest.TestCase):
+    def test_dat_round_trip_preserves_all_levels(self):
+        levels = []
+        for level_index in range(maze.DEFAULT_LEVELS_PER_DAT_FILE):
+            level = maze.create_level()
+            level[1][1] = maze.MAP_EMPTY
+            level[1][2] = maze.MAP_EMPTY
+            level[2][1] = maze.MAP_TUNNEL
+            level[2][2] = level_index % 3
+            level[3][3] = (level_index + 1) % 3
+            levels.append(level)
+
+        with tempfile.TemporaryDirectory() as tmp_dir:
+            dat_path = Path(tmp_dir) / "roundtrip.dat"
+            maze.save_dat_levels(dat_path, levels)
+            loaded = maze.load_dat_levels(dat_path)
+
+        self.assertEqual(levels, loaded)
+
+    def test_dat_level_count_is_derived_from_file_size(self):
+        levels = [maze.create_level() for _ in range(3)]
+
+        with tempfile.TemporaryDirectory() as tmp_dir:
+            dat_path = Path(tmp_dir) / "three-levels.dat"
+            maze.save_dat_levels(dat_path, levels)
+
+            self.assertEqual(maze.get_dat_level_count(dat_path), 3)
+            self.assertEqual(maze.get_level_count(dat_path), 3)
+            self.assertEqual(maze.load_dat_level(dat_path, 4), levels[1])
+
+    def test_load_json_level_supports_legacy_boolean_maps(self):
+        legacy_map = [
+            [True, False, True],
+            [False, False, True],
+        ]
+
+        with tempfile.TemporaryDirectory() as tmp_dir:
+            json_path = Path(tmp_dir) / "legacy.json"
+            json_path.write_text(json.dumps(legacy_map), encoding="utf-8")
+            loaded = maze.load_json_level(json_path)
+
+        self.assertEqual(
+            loaded,
+            [
+                [maze.MAP_WALL, maze.MAP_TUNNEL, maze.MAP_WALL],
+                [maze.MAP_TUNNEL, maze.MAP_TUNNEL, maze.MAP_WALL],
+            ],
+        )
+
+    def test_load_json_level_preserves_exact_tile_values(self):
+        tile_map = [
+            [maze.MAP_EMPTY, maze.MAP_WALL, maze.MAP_TUNNEL],
+            [maze.MAP_TUNNEL, maze.MAP_EMPTY, maze.MAP_WALL],
+        ]
+
+        with tempfile.TemporaryDirectory() as tmp_dir:
+            json_path = Path(tmp_dir) / "tiles.json"
+            maze.save_json_level(json_path, tile_map)
+            loaded = maze.load_json_level(json_path)
+
+        self.assertEqual(tile_map, loaded)
+
+
+if __name__ == "__main__":
+    unittest.main()