using NUnit.Framework; using System.Collections.Generic; [TestFixture] public class MyTests { [Test] public void TestAddItem() { ListIn this example, we create an empty list of integers using the List class from the System.Collections.Generic namespace. We then call the AddItem method on this list, passing in the value 42. We assert that the count of the list is now 1, that the index of the added item is 0, and that the value of the added item is 42. The List.AddItem method is part of the NUnit.Framework package, which you can install using NuGet. To add this package to your project in Visual Studio, you can right-click on your project in the Solution Explorer, choose "Manage NuGet Packages", and search for "NUnit.Framework".myList = new List (); int index = myList.AddItem(42); Assert.AreEqual(1, myList.Count); Assert.AreEqual(0, index); Assert.AreEqual(42, myList[0]); } }