public void AddWhenExistsNonGeneric()
{
//Prepare
var list = new ArrayList();
list.Add("banana");
list.Add("apple");
//Act
list.AddIfNotExists("apple");
//Assert
Assert.AreEqual(list.Count, 2);
Assert.AreEqual(list[0], "banana");
Assert.AreEqual(list[1], "apple");
}