private void ValidateCart(CartResponse cart, string userId, string productId, int quantity)
{
cart.Should().NotBeNull();
cart.UserId.Should().BeEquivalentTo(testUserId);
cart.Items.Should().NotBeNullOrEmpty();
cart.TotalPrice.Should().BeGreaterThan(0);
var product = cart.Items.FirstOrDefault(w => w.Id == ObjectId.Parse(productId));
product.Should().NotBeNull();
product.Quantity.Should().BeGreaterOrEqualTo(quantity);
}
