maui-linux/Xamarin.Forms.Core.UnitTests/BehaviorTest.cs

using System;
using NUnit.Framework;

namespace Xamarin.Forms.Core.UnitTests
{
	class MockBehavior<T> : Behavior<T> where T:BindableObject
	{
		public static int AttachCount { get; set; }
		public bool attached;
		public bool detached;

		protected override void OnAttachedTo (BindableObject bindable)
		{
			base.OnAttachedTo (bindable);
			attached = true;
			AttachCount++;
			AssociatedObject = bindable;
		}

		protected override void OnDetachingFrom (BindableObject bindable)
		{
			AttachCount--;
			detached = true;
			base.OnDetachingFrom (bindable);
			AssociatedObject = null;
		}

		public BindableObject AssociatedObject {get;set;}
	}

	[TestFixture]
	public class BehaviorTest : BaseTestFixture
	{
		[Test]
		public void AttachAndDetach ()
		{
			var behavior = new MockBehavior<MockBindable> ();
			var bindable = new MockBindable ();

			Assert.False (behavior.attached);
			Assert.False (behavior.detached);
			Assert.Null (behavior.AssociatedObject);

			((IAttachedObject)behavior).AttachTo (bindable);

			Assert.True (behavior.attached);
			Assert.False (behavior.detached);
			Assert.AreSame (bindable, behavior.AssociatedObject);

			((IAttachedObject)behavior).DetachFrom (bindable);

			Assert.True (behavior.attached);
			Assert.True (behavior.detached);
			Assert.Null (behavior.AssociatedObject);
		}

		[Test]
		public void AttachToTypeCompatibleWithTargetType ()
		{
			var behavior = new MockBehavior<MockBindable> ();
			var bindable = new View ();

			Assert.Throws<InvalidOperationException> (() => ((IAttachedObject)behavior).AttachTo (bindable));
		}
			
		[Test]
		public void BehaviorsInCollectionAreAttachedWhenCollectionIsAttached ()
		{
			var behavior = new MockBehavior<MockBindable> ();
			var collection = new AttachedCollection<Behavior> ();
			var bindable = new MockBindable ();
			collection.Add (behavior);
			Assert.Null (behavior.AssociatedObject);

			((IAttachedObject)collection).AttachTo (bindable);
			Assert.AreSame (bindable, behavior.AssociatedObject);

			((IAttachedObject)collection).DetachFrom (bindable);
			Assert.Null (behavior.AssociatedObject);
		}

		[Test]
		public void BehaviorsAddedToAttachedCollectionAreAttached ()
		{
			var behavior = new MockBehavior<MockBindable> ();
			var collection = new AttachedCollection<Behavior> ();
			var bindable = new MockBindable ();
			((IAttachedObject)collection).AttachTo (bindable);
			Assert.Null (behavior.AssociatedObject);

			collection.Add (behavior);
			Assert.AreSame (bindable, behavior.AssociatedObject);

			collection.Remove (behavior);
			Assert.Null (behavior.AssociatedObject);
		}

		[Test]
		public void TestBehaviorsAttachedDP ()
		{
			var behavior = new MockBehavior<MockBindable> ();
			var bindable = new MockBindable ();
			var collection = bindable.Behaviors;
			Assert.Null (behavior.AssociatedObject);

			collection.Add (behavior);
			Assert.AreSame (bindable, behavior.AssociatedObject);

			collection.Remove (behavior);
			Assert.Null (behavior.AssociatedObject);
		}

		[Test]
		//https://bugzilla.xamarin.com/show_bug.cgi?id=44074
		public void TestBehaviorsAreDetachedBeforeGarbageCollection()
		{
			WeakReference weakBindable = null;

			var attachCount = MockBehavior<VisualElement>.AttachCount;

			int i = 0;
			Action create = null;
			create = () =>
			{
				if (i++ < 1024)
				{
					create();
					return;
				}

				var bindable = new MockBindable
				{
					Behaviors = {
						new MockBehavior<VisualElement> ()
					}
				};
				weakBindable = new WeakReference(bindable);
			};

			create();

			GC.Collect();
			GC.WaitForPendingFinalizers();
			GC.Collect();

			Assert.False(weakBindable.IsAlive);
			Assert.AreEqual(attachCount, MockBehavior<VisualElement>.AttachCount);
		}
	}
}