code: def test_1_send_message(self, mock_post):
      mock_post.return_value.status_code = 200
      self.handler.send_message("#test-channel", "Test message")
      mock_post.assert_called_with(
          "https://slack.com/api/chat.postMessage",
          headers={"Authorization": "Bearer test-slack-token"},
          json={"channel": "#test-channel", "text": "Test message"},
      )
  
imports: from mindsdb.integrations.handlers.slack_handler import SlackHandler
  import unittest
  from unittest.mock import patch
label_desc: Use image node_id 3 for calling the SlackHandlerTest obj's underlying member method code with example usage: obj.test_1_send_message(mock_post) without return types