How to test store_items function mocking Object

def store_items(self):
    items_json = json.dumps(self.items, default=self.serialize_date).encode("utf-8")
    self.algorithm.ObjectStore.SaveBytes(self.trade_planning_key, items_json)
    self.algorithm.Debug(f"Stored {len(self.items)} items in ObjectStore under tag '{self.trade_planning_key}'.")

Example 

import unittest
from unittest.mock import MagicMock
    def setUp(self):
        self.algorithm = MagicMock()
        self.object_storage = ObjectStorageManagement(self.algorithm)
        self.mock_data = [
            {
                "Rank": 1,
                "EffectiveDate": "2023-01-01",