The SlackAPIFileOperator is not straight forward and it might be better to add an example DAG to demonstrate the usage.

tests/providers/slack/operators/test_slack.py
test_token = 'test_token'
        test_slack_conn_id = 'test_slack_conn_id'
        slack_api_post_operator = self.__construct_operator(test_token, None, self.test_api_params)
        assert slack_api_post_operator.token == test_token
        assert slack_api_post_operator.slack_conn_id is None
        assert slack_api_post_operator.method == self.expected_method
        assert slack_api_post_operator.text == self.test_text
        assert slack_api_post_operator.channel == self.test_channel
        assert slack_api_post_operator.api_params == self.test_api_params
        assert slack_api_post_operator.username == self.test_username
        assert slack_api_post_operator.icon_url == self.test_icon_url
        assert slack_api_post_operator.attachments == self.test_attachments
        assert slack_api_post_operator.blocks == self.test_blocks
        slack_api_post_operator = self.__construct_operator(None, test_slack_conn_id)
        assert slack_api_post_operator.token is None
        assert slack_api_post_operator.slack_conn_id == test_slack_conn_id
    @mock.patch('airflow.providers.slack.operators.slack.SlackHook')
    def test_api_call_params_with_default_args(self, mock_hook):