Improve type system and test coverage for custom memory storage

Co-Authored-By: Joe Moura <joao@crewai.com>

tests/memory/long_term_memory_test.py

@@ -7,7 +7,31 @@ from crewai.memory.long_term.long_term_memory_item import LongTermMemoryItem
 @pytest.fixture
 def long_term_memory():
     """Fixture to create a LongTermMemory instance"""
-    return LongTermMemory()
+    # Create a mock storage for testing
+    from crewai.memory.storage.interface import Storage
+    
+    class MockStorage(Storage):
+        def __init__(self):
+            self.data = []
+            
+        def save(self, value, metadata):
+            self.data.append({"value": value, "metadata": metadata})
+            
+        def search(self, query, limit=3, score_threshold=0.35):
+            return [
+                {
+                    "context": item["value"],
+                    "metadata": item["metadata"],
+                    "score": 0.5,
+                    "datetime": item["metadata"].get("datetime", "test_datetime")
+                }
+                for item in self.data
+            ]
+            
+        def reset(self):
+            self.data = []
+            
+    return LongTermMemory(storage=MockStorage())
 
 
 def test_save_and_search(long_term_memory):