Try It Yourself - SyntaxStudy Editor

HTML / CSS / JS

// NUnit tests — TestFixture, SetUp, TearDown, and constraint model

using NUnit.Framework;
using System.Collections.Generic;

[TestFixture]
public class ShoppingCartTests
{
    private ShoppingCart _cart = null!;

[SetUp]
    public void BeforeEachTest()
    {
        _cart = new ShoppingCart();
    }

[TearDown]
    public void AfterEachTest()
    {
        _cart.Clear();
    }

[Test]
    public void AddItem_NewItem_IncreasesCount()
    {
        _cart.Add(new CartItem("Widget", 9.99m, 1));
        Assert.That(_cart.Count, Is.EqualTo(1));
    }

[Test]
    public void Total_MultipleItems_SumsCorrectly()
    {
        _cart.Add(new CartItem("Widget", 10m, 2));
        _cart.Add(new CartItem("Gadget", 25m, 1));
        Assert.That(_cart.Total, Is.EqualTo(45m).Within(0.001m));
    }

[TestCase(0,   0m)]
    [TestCase(1,  10m)]
    [TestCase(3,  30m)]
    public void Total_VaryingQuantities_CalculatesCorrectly(int qty, decimal expected)
    {
        _cart.Add(new CartItem("X", 10m, qty));
        Assert.That(_cart.Total, Is.EqualTo(expected));
    }

[Test]
    public void Remove_ExistingItem_RemovesFromCart()
    {
        _cart.Add(new CartItem("Widget", 10m, 1));
        _cart.Remove("Widget");
        Assert.That(_cart.Count, Is.Zero);
    }

[Test]
    public void Remove_NonExistentItem_ThrowsKeyNotFoundException()
    {
        Assert.That(() => _cart.Remove("Ghost"),
            Throws.TypeOf<KeyNotFoundException>());
    }
}

// Domain classes (would live in your main project)
record CartItem(string Name, decimal Price, int Qty);

class ShoppingCart
{
    private readonly List<CartItem> _items = new();
    public int     Count => _items.Count;
    public decimal Total => _items.Sum(i => i.Price * i.Qty);
    public void    Add(CartItem item) => _items.Add(item);
    public void    Clear()            => _items.Clear();
    public void    Remove(string name)
    {
        var item = _items.FirstOrDefault(i => i.Name == name)
            ?? throw new KeyNotFoundException(name);
        _items.Remove(item);
    }
}