def METHOD_NAME(
    m_format_validator, minimal_swagger_spec,
):
    prop_schema = {
        'x-nullable': True,
        'type': 'string',
        'format': 'url',
    }
    list(
        format_validator(
            minimal_swagger_spec,
            validator=None,
            format=prop_schema['format'],
            instance=None,  # property value
            schema=prop_schema,
        ),
    )
    assert m_format_validator.call_count == 0