Edit in JSFiddle

describe('A Cart with a several different products', function () {
    var cart;
 
    beforeEach(function () {
        cart = Cart.create();
    });
 
    it('must have a #grossPriceSum() of the contained products', function () {
        var product = Product.create('A', 10),
            book = Book.create('B', 100);
 
        cart.add(product);
        cart.add(book);
 
        expect(cart.grossPriceSum()).toEqual(132);
    });
});