Sylius\Behat\Page\Shop\Cart\SummaryPageInterface::getPromotionCouponValidationMessage PHP Method

    public function getPromotionCouponValidationMessage();

 /**
  * @Then I should be notified that the coupon is invalid
  */
 public function iShouldBeNotifiedThatCouponIsInvalid()
 {
     Assert::same($this->summaryPage->getPromotionCouponValidationMessage(), 'Coupon code is invalid.');
 }