Omnipay\Common\CreditCard::setPhoneExtension PHP Method

    public function setPhoneExtension($value)
    {
        $this->setParameter('billingPhoneExtension', $value);
        $this->setParameter('shippingPhoneExtension', $value);
        return $this;
    }

 public function testPhoneExtension()
 {
     $this->card->setPhoneExtension('001');
     $this->assertEquals('001', $this->card->getPhoneExtension());
     $this->assertEquals('001', $this->card->getBillingPhoneExtension());
     $this->assertEquals('001', $this->card->getShippingPhoneExtension());
 }