code: def test_send(self, patch):
      def _conversations_list(params={}):
          return _slack_response(
              token="valid",
              data={
                  "ok": True,
                  "channels": [{"name": "valid", "id": "valid_id"}],
                  "response_metadata": {"next_cursor": ""},
              },
          )
  
      def _api_call(method, data={}):
          assert method == "files.upload"
          return {"ok": False, "error": "error_reason"}
  
      mock_client = MagicMock()
      mock_client.conversations_list = MagicMock(
          side_effect=_conversations_list
      )
      mock_client.api_call = MagicMock(side_effect=_api_call)
      patch.return_value = mock_client
  
      api = gokart.slack.SlackAPI(
          token="valid", channel="valid", to_user="test user"
      )
      api.send_snippet(comment="test", title="title", content="content")
  
file_path: gokart/test/slack/test_slack_api.py
imports: import unittest
  from logging import getLogger
  from unittest import mock
  from unittest.mock import MagicMock
  from slack_sdk import WebClient
  from slack_sdk.web.slack_response import SlackResponse
  from testfixtures import LogCapture
  import gokart.slack
label_desc: Use image node_id 4 for calling the TestSlackAPI obj's underlying member method code with example usage: obj.test_send(patch) and returns: _slack_response, dict