Flintstone\Config::setFormatter PHP Method

    public function setFormatter($formatter)
    {
        if ($formatter === null) {
            $formatter = new SerializeFormatter();
        }
        if (!$formatter instanceof FormatterInterface) {
            throw new Exception('Formatter must be an instance of Flintstone\\Formatter\\FormatterInterface');
        }
        $this->config['formatter'] = $formatter;
    }

 /**
  * @expectedException Flintstone\Exception
  */
 public function testConfigInvalidFormatter()
 {
     $config = new Config();
     $config->setFormatter(new self());
 }