test.cs

[Fact]
        public void Inserting_Items_Should_Update_Containers()
        {
            var target = CreateTarget(itemCount: 20);

            target.ApplyTemplate();
            target.Measure(new Size(100, 95));
            target.Arrange(new Rect(0, 0, 100, 95));

            ((ILogicalScrollable)target).Offset = new Vector(0, 5);

            var expected = Enumerable.Range(5, 10).Select(x => $"Item {x}").ToList();
            var items = (ObservableCollection<string>)target.Items;

            Assert.Equal(
                expected,
                target.Panel.Children.Select(x => x.DataContext));

            items.Insert(6, "Inserted");
            expected.Insert(1, "Inserted");

            Assert.Equal(
                expected,
                target.Panel.Children.Select(x => x.DataContext));
        }