def test_download_file_proxies_to_transfer_object(self): with mock.patch('boto3.s3.inject.S3Transfer') as transfer: inject.download_file( mock.sentinel.CLIENT, Bucket='bucket', Key='key', Filename='filename') transfer.return_value.download_file.assert_called_with( bucket='bucket', key='key', filename='filename', extra_args=None, callback=None)