def METHOD_NAME(self):
    too_small = 1 * 1024 * 1024
    self.stat_mock.return_value.st_size = 1024 * 1024 * 1024
    uploader = ConcurrentUploader(mock.Mock(), 'vault_name',
                                  part_size=too_small)
    total_parts, part_size = uploader._calculate_required_part_size(
        1024 * 1024 * 1024)
    self.assertEqual(total_parts, 256)
    # Part size if 4MB not the passed in 1MB.
    self.assertEqual(part_size, 4 * 1024 * 1024)