create MemoryGameBoardStore Class and rework Building of Game Board Storage

tests/test_GameStateStore.py

@@ -1,10 +1,12 @@
 import unittest
+from typing import Any, cast
 
 from server.GameBoard import GameBoard
-from server.GameStateStore import GameStateStore
+from server.game_board_stats import GameBoardStoreBuilder
+from server.game_board_stats.MemoryGameBoardStore import MemoryGameBoardStore
+from server.game_board_stats.RedisGameBoardStore import RedisGameBoardStore
 from snakes.TemplateSnake import TemplateSnake
 
-
 class _FakeRedis:
   def __init__(self):
     self.data = {}
@@ -70,21 +72,33 @@ class TestGameStateStore(unittest.IsolatedAsyncioTestCase):
     )
     return board
 
-  async def test_memory_backend_returns_none(self):
-    store = GameStateStore(backend="memory")
+  def test_builder_selects_store_backend(self):
+    memory_store = GameBoardStoreBuilder.build(backend="memory")
+    redis_store = GameBoardStoreBuilder.build(backend="redis")
+    default_store = GameBoardStoreBuilder.build(backend="unknown")
+
+    self.assertIsInstance(memory_store, MemoryGameBoardStore)
+    self.assertIsInstance(redis_store, RedisGameBoardStore)
+    self.assertIsInstance(default_store, MemoryGameBoardStore)
+
+  async def test_memory_backend_roundtrip(self):
+    store = MemoryGameBoardStore()
     board = self._build_board()
     await store.save("game-1", board)
 
-    loaded = await store.load("game-1")
-    self.assertIsNone(loaded)
+    loaded = cast(GameBoard, await store.load("game-1"))
+    self.assertIsNotNone(loaded)
+    self.assertEqual(loaded.id, "game-1")
+    await store.delete("game-1")
+    self.assertIsNone(await store.load("game-1"))
 
   async def test_redis_backend_roundtrip(self):
-    store = GameStateStore(backend="redis")
-    store._redis = _FakeRedis()
+    store = RedisGameBoardStore()
+    store._redis = cast(Any, _FakeRedis())
     board = self._build_board()
 
     await store.save("game-1", board)
-    loaded = await store.load("game-1")
+    loaded = cast(GameBoard, await store.load("game-1"))
     self.assertIsNotNone(loaded)
     self.assertEqual(loaded.id, "game-1")
     self.assertEqual(loaded.get_turn(), 3)