public function testTokenResponse()
    {
        $Response = TokenResponse::initializeByString('{
"id": "11fe4b4d430eccc4ca59b8df31bc5d161b4d54020082362a7d389486f5349066",
"expiresAt": "2015-05-22T11:21:37+03:00",
"card": {
"lastFour": "4242",
"mask": "************4242",
"type": "visa",
"expirationMonth": "4",
"expirationYear": "2020" }
}');
        $this->assertEquals('11fe4b4d430eccc4ca59b8df31bc5d161b4d54020082362a7d389486f5349066', $Response->getId());
        $this->assertEquals(1432282897, $Response->getExpiresAt());
        $this->assertEquals('4242', $Response->getCard()->getLastFour());
        $this->assertEquals('************4242', $Response->getCard()->getMask());
        $this->assertEquals(4, $Response->getCard()->getExpirationMonth());
        $this->assertEquals(2020, $Response->getCard()->getExpirationYear());
        $this->assertEquals('token\'s data
    id:        11fe4b4d430eccc4ca59b8df31bc5d161b4d54020082362a7d389486f5349066
    expiresAt: 2015-05-22T08:21:37+0000
    card
        four:       4242
        mask:       ************4242
        type:       visa
        exp. month: 4
        exp. year:  2020', (string) $Response);
    }
 /**
  * REST API method card/getToken implementation
  * @param string $number credit card's number
  * @param int $expirationMonth credit card's expiration month, without leading zero
  * @param int $expirationYear credit card's expiration year (4 digits)
  * @param string $securityCode credit card's security code: CVC, CVV2
  * @param null|string $callback callback function name for JSONP
  * @return Request card/getToken request instance
  * @throws ErrorException if there is an API error
  */
 public function cardGetToken($number, $expirationMonth, $expirationYear, $securityCode, $callback = null)
 {
     $parameters = ['number' => (string) $number, 'expiration_month' => (int) $expirationMonth, 'expiration_year' => (int) $expirationYear, 'security_code' => (string) $securityCode];
     if (!is_null($callback)) {
         $parameters['callback'] = (string) $callback;
     }
     return $this->getRequest('card/getToken', $parameters, function ($string) {
         return TokenResponse::initializeByString($string);
     });
 }