def METHOD_NAME(self, mock_get):
    mock_get.return_value.status_code = 200
    mock_get.return_value.json.return_value = [{"sha": "123"}, {"sha": "456"}]
    github_api = GithubHelper('access_token', 'username')
    result = github_api.get_latest_commit_id_of_pull_request("owner", "repo", 1)
    self.assertEqual(result, "456")