diff --git a/tests/conftest.py b/tests/conftest.py
index ff87c6f..462d701 100644
--- a/tests/conftest.py
+++ b/tests/conftest.py
@@ -21,6 +21,16 @@ def temp_dir():
     shutil.rmtree(dirpath)
 
 
+@pytest.fixture(autouse=True)
+def mock_memory_storage_dir(monkeypatch):
+    """Override MEMORY_STORAGE_DIR for all tests to use a temp directory."""
+    test_dir = tempfile.mkdtemp()
+    monkeypatch.setenv("MEMORY_STORAGE_DIR", test_dir)
+    yield
+    # Cleanup
+    shutil.rmtree(test_dir, ignore_errors=True)
+
+
 @pytest.fixture
 def memory(temp_dir):
     """Create a fresh Memory instance for testing."""