def METHOD_NAME(self):
    self.vault.DefaultPartSize = 2 * 1024 * 1024
    self.vault.create_archive_writer = mock.Mock()
    self.getsize.return_value = 1
    with mock.patch('boto.glacier.vault.open', self.mock_open,
                    create=True):
        self.vault.create_archive_from_file('myfile')
    # The write should be created with the default part size of the
    # instance (2 MB).
    self.vault.create_archive_writer.assert_called_with(
        description=mock.ANY, part_size=self.vault.DefaultPartSize)