JMathai\PhpMultiCurl\MultiCurl::getInstance PHP Method

    public static function getInstance()
    {
        if (self::$inst == null) {
            self::$singleton = 1;
            self::$inst = new MultiCurl();
        }
        return self::$inst;
    }

 public function testResponseHeaders()
 {
     $mc = MultiCurl::getInstance();
     $google = $mc->addUrl('http://www.example.com/404');
     $this->assertInternalType('array', $google->headers);
     $this->assertNotEmpty($google->headers['Etag']);
 }