public function it_generates_invoice_number_based_on(OrderInterface $order, PaymentInterface $payment)
 {
     $order->getId()->willReturn('001');
     $payment->getId()->willReturn('1');
     $this->generate($order, $payment)->shouldReturn('001-1');
 }
 /**
  * {@inheritdoc}
  */
 public function generate(OrderInterface $order, PaymentInterface $payment)
 {
     return $order->getId() . '-' . $payment->getId();
 }