Imagine we have this website.

now let’s login.

now let’s try to buy an item

notice that we got not enough store credit.

now let’s analysis the request.

now let’s see the cart after adding the quantity.

as we see we can add the quantity to the cart using this request

but what if we set the quantity to negative number?

now let’s refresh the cart.

notice that we have now the total set to 1337 so let’s try to buy the item

notice that the message said that the total can’t be zero.

so let’s try to make the quantity 1