<?php
function it_returns_total_quantity_in_cart(CartItem $cartItem1, CartItem $cartItem2, ..., CartItemQuantity $cartItemQuantity, ...)
    {
        $cartItemQuantity->asInt()->willReturn(3);
        $cartItem1->beConstructedWith([..., $cartItemQuantity->getWrappedObject(), ...]);
        $cartItem1->getQuantity()->willReturn($cartItemQuantity);
        $this->add($cartItem1);
        $this->add($cartItem2);
        $this->getTotalQuantity()->shouldReturn(3);
    }
//
//it returns total quantity in cart
//      exception [err:TypeError("Return value of Double\App\Domain\Webshop\CartItem\P7::getQuantity() must be an instance of //App\Domain\Webshop\CartItemQuantity, null returned")] has been thrown.
?>