public function testCheckCode()
{
$secret = '4FDAGLLSP6BIVU5H';
$time = 1375000339;
$code = $this->totp->getCode($secret, $time);
$codePrev = $this->totp->getCode($secret, $time - 30);
$codeNext = $this->totp->getCode($secret, $time + 30);
$this->assertTrue($this->totp->checkCode($secret, $code, $time));
$this->assertTrue($this->totp->checkCode($secret, $codePrev, $time));
$this->assertTrue($this->totp->checkCode($secret, $codeNext, $time));
}