diff --git a/cognee/tests/unit/modules/retrieval/conversation_history_test.py b/cognee/tests/unit/modules/retrieval/conversation_history_test.py
index 43577cb7a..1ffa5007d 100644
--- a/cognee/tests/unit/modules/retrieval/conversation_history_test.py
+++ b/cognee/tests/unit/modules/retrieval/conversation_history_test.py
@@ -1,6 +1,5 @@
 import pytest
-from unittest.mock import AsyncMock, patch
-from cognee.modules.users.methods import get_default_user
+from unittest.mock import AsyncMock, patch, MagicMock
 from cognee.context_global_variables import session_user
 
 
@@ -17,13 +16,20 @@ def create_mock_cache_engine(qa_history=None):
     return mock_cache
 
 
+def create_mock_user():
+    """Create a mock user without database access"""
+    mock_user = MagicMock()
+    mock_user.id = "test-user-id-123"
+    return mock_user
+
+
 class TestConversationHistoryUtils:
     """Test the two utility functions: get_conversation_history and save_to_session_cache"""
 
     @pytest.mark.asyncio
     async def test_get_conversation_history_returns_empty_when_no_history(self):
         """Test get_conversation_history returns empty string when no history exists."""
-        user = await get_default_user()
+        user = create_mock_user()
         session_user.set(user)
 
         mock_cache = create_mock_cache_engine([])
@@ -41,7 +47,7 @@ class TestConversationHistoryUtils:
     @pytest.mark.asyncio
     async def test_get_conversation_history_formats_history_correctly(self):
         """Test get_conversation_history formats Q&A history with correct structure."""
-        user = await get_default_user()
+        user = create_mock_user()
         session_user.set(user)
 
         mock_history = [
@@ -71,7 +77,7 @@ class TestConversationHistoryUtils:
     @pytest.mark.asyncio
     async def test_save_to_session_cache_saves_correctly(self):
         """Test save_to_session_cache calls add_qa with correct parameters."""
-        user = await get_default_user()
+        user = create_mock_user()
         session_user.set(user)
 
         mock_cache = create_mock_cache_engine([])
@@ -97,3 +103,28 @@ class TestConversationHistoryUtils:
             assert call_kwargs["context"] == "Python is a programming language"
             assert call_kwargs["answer"] == "Python is a high-level programming language"
             assert call_kwargs["session_id"] == "my_session"
+
+    @pytest.mark.asyncio
+    async def test_save_to_session_cache_uses_default_session_when_none(self):
+        """Test save_to_session_cache uses 'default_session' when session_id is None."""
+        user = create_mock_user()
+        session_user.set(user)
+
+        mock_cache = create_mock_cache_engine([])
+
+        with patch(
+            "cognee.infrastructure.databases.cache.get_cache_engine.get_cache_engine",
+            return_value=mock_cache,
+        ):
+            from cognee.modules.retrieval.utils.session_cache import save_to_session_cache
+
+            result = await save_to_session_cache(
+                query="Test question",
+                context_summary="Test context",
+                answer="Test answer",
+                session_id=None,
+            )
+
+            assert result is True
+            call_kwargs = mock_cache.add_qa.call_args.kwargs
+            assert call_kwargs["session_id"] == "default_session"