public function testZerofill()
{
$this->assertEquals('0000000001', Utils::zerofill(1, 10));
}
/**
* @param string
* @param string
* @return string Concatenated key and mac
*/
protected function composeCode($key, $mac)
{
return Utils::zerofill($key, $this->getKeyLength()) . substr($mac, 0, $this->getMacLength());
}