def METHOD_NAME(self, event):
    event.app.cache.get_available_guild.return_value = None
    result = event.get_guild()
    assert result is event.app.cache.get_unavailable_guild.return_value
    event.app.cache.get_unavailable_guild.assert_called_once_with(789)
    event.app.cache.get_available_guild.assert_called_once_with(789)