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

    public function isSingleItemOnPage();

 /**
  * @Then there should be one item in my cart
  */
 public function thereShouldBeOneItemInMyCart()
 {
     Assert::true($this->summaryPage->isSingleItemOnPage(), 'There should be only one item on list, but it does not.');
 }