Xamarin.Forms/Xamarin.Forms.Core.UnitTests/ElementTests.cs

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

namespace Xamarin.Forms.Core.UnitTests
{
	public class TestElement
		: Element
	{
		public TestElement ()
		{
			internalChildren.CollectionChanged += OnChildrenChanged;
		}

		void OnChildrenChanged (object sender, NotifyCollectionChangedEventArgs e)
		{
			if (e.NewItems != null) {
				foreach (Element element in e.NewItems)
					OnChildAdded (element);
			}

			if (e.OldItems != null) {
				foreach (Element element in e.OldItems)
					OnChildRemoved (element);
			}
		}

		public IList<Element> Children
		{
			get { return internalChildren; }
		}

		internal override ReadOnlyCollection<Element> LogicalChildrenInternal
		{
			get { return new ReadOnlyCollection<Element> (internalChildren); }
		}

		readonly ObservableCollection<Element> internalChildren = new ObservableCollection<Element> ();
	}

	[TestFixture]
	public class ElementTests
		: BaseTestFixture
	{
		[Test]
		public void DescendantAddedLevel1 ()
		{
			var root = new TestElement();

			var child = new TestElement();

			bool added = false;
			root.DescendantAdded += (sender, args) => {
				Assert.That (args.Element, Is.SameAs (child));
				added = true;
			};

			root.Children.Add (child);
		}

		[Test]
		public void DescendantAddedLevel2 ()
		{
			var root = new TestElement();

			var child = new TestElement();
			root.Children.Add (child);

			var child2 = new TestElement();

			bool added = false;
			root.DescendantAdded += (sender, args) => {
				Assert.That (args.Element, Is.SameAs (child2));
				added = true;
			};

			child.Children.Add (child2);
		}

		[Test]
		public void DescendantAddedExistingChildren ()
		{
			var root = new TestElement();

			var tier2 = new TestElement();

			var child = new TestElement {
				Children = {
					tier2
				}
			};

			bool tier1added = false;
			bool tier2added = false;
			root.DescendantAdded += (sender, args) => {
				if (!tier1added)
					tier1added = ReferenceEquals (child, args.Element);
				if (!tier2added)
					tier2added = ReferenceEquals (tier2, args.Element);
			};

			root.Children.Add (child);

			Assert.That (tier1added, Is.True);
			Assert.That (tier2added, Is.True);
		}

		[Test]
		public void DescendantRemovedLevel1 ()
		{
			var root = new TestElement();

			var child = new TestElement();
			root.Children.Add (child);

			bool removed = false;
			root.DescendantRemoved += (sender, args) => {
				Assert.That (args.Element, Is.SameAs (child));
				removed = true;
			};

			root.Children.Remove (child);
		}

		[Test]
		public void DescendantRemovedLevel2 ()
		{
			var root = new TestElement();

			var child = new TestElement();
			root.Children.Add (child);

			var child2 = new TestElement();
			child.Children.Add (child2);

			bool removed = false;
			root.DescendantRemoved += (sender, args) => {
				Assert.That (args.Element, Is.SameAs (child2));
				removed = true;
			};

			child.Children.Remove (child2);
		}

		[Test]
		public void DescendantRemovedWithChildren ()
		{
			var root = new TestElement();

			var tier2 = new TestElement();

			var child = new TestElement {
				Children = {
					tier2
				}
			};

			root.Children.Add (child);

			bool tier1removed = false;
			bool tier2removed = false;
			root.DescendantRemoved += (sender, args) => {
				if (!tier1removed)
					tier1removed = ReferenceEquals (child, args.Element);
				if (!tier2removed)
					tier2removed = ReferenceEquals (tier2, args.Element);
			};

			root.Children.Remove (child);

			Assert.That (tier1removed, Is.True);
			Assert.That (tier2removed, Is.True);
		}
	}
}