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

using System;
using NUnit.Framework;

namespace Xamarin.Forms.Core.UnitTests
{
	public abstract class CommandSourceTests<T> : BaseTestFixture
		where T : BindableObject
	{
		[Test]
		public void TestCommand ()
		{
			var source = CreateSource();

			bool executed = false;
			source.SetValue (CommandProperty, new Command (o => {
				executed = true;
				Assert.AreEqual (source, o);
			}));

			source.SetValue (CommandParameterProperty, source);

			Activate (source);

			Assert.True (executed);
		}

		[Test]
		public void CommandCanExecuteModifiesEnabled ([Values(true, false)] bool initial)
		{
			bool canExecute = initial;
			Command command;
			var source = CreateSource();
			source.SetValue (CommandProperty, command = new Command (() => { }, () => canExecute));

			Assert.AreEqual (canExecute, source.GetValue (IsEnabledProperty));

			canExecute = !initial;
			command.ChangeCanExecute ();

			Assert.AreEqual (canExecute, source.GetValue (IsEnabledProperty));
		}

		[Test]
		public void ReenabledAfterCommandRemoved()
		{
			var source = CreateSource();
			source.SetValue (CommandProperty, new Command (() => { }, () => false));

			Assert.That (source.GetValue (IsEnabledProperty), Is.False);

			source.SetValue (CommandProperty, null);

			Assert.That (source.GetValue (IsEnabledProperty), Is.True);
		}

		[Test]
		public void CommandUnhooksOnNull ()
		{
			bool canExecute = false;
			Command command;
			var source = CreateSource();

			bool raised = false;
			source.SetValue (CommandProperty, command = new Command (() => { }, () => {
				raised = true;
				return canExecute;
			}));

			raised = false;
			source.SetValue (CommandProperty, null);

			canExecute = true;
			command.ChangeCanExecute ();

			Assert.False (raised);
		}

		[Test]
		public void CommandCanExecuteInvokedOnCommandSet ()
		{
			bool fired = false;
			Func<bool> canExecute = () => {
				fired = true;
				return true;
			};

			Assert.IsFalse (fired);
			var source = CreateSource();
			source.SetValue (CommandProperty, new Command (() => { }, canExecute));

			Assert.True (fired);
		}

		[Test]
		public void CommandCanExecuteInvokedOnCommandParameterSet ()
		{
			bool fired;
			Func<bool> canExecute = () => {
				fired = true;
				return true;
			};

			var source = CreateSource();
			source.SetValue (CommandProperty, new Command (() => { }, canExecute));

			fired = false;
			Assert.IsFalse (fired);
			source.SetValue (CommandParameterProperty, new object ());
			Assert.True (fired);
		}

		[Test]
		public void CommandCanExecuteInvokedOnChange()
		{
			bool fired;
			Func<bool> canExecute = () => {
				fired = true;
				return true;
			};

			var cmd = new Command (() => { }, canExecute);
			var source = CreateSource();
			source.SetValue (CommandProperty, cmd);

			fired = false;
			
			cmd.ChangeCanExecute();

			Assert.That (fired, Is.True, "CanExecute was not called when the event was raised");
		}

		class BoolViewModel
			: MockViewModel
		{
			bool toggle;

			public bool Toggle
			{
				get { return toggle; }
				set
				{
					if (toggle == value)
						return;

					toggle = value;
					OnPropertyChanged();
				}
			}
		}

		[Test]
		public void EnabledUpdatesDoNotRemoveBindings()
		{
			var vm = new BoolViewModel { Toggle = true };
			var source = CreateSource();
			source.BindingContext = vm;
			source.SetBinding (IsEnabledProperty, "Toggle");

			Assert.That (source.GetValue (IsEnabledProperty), Is.True);

			source.SetValue (CommandProperty, new Command (() => { }));

			Assert.That (source.GetIsBound (IsEnabledProperty), Is.True);
		}

		protected abstract T CreateSource();
		protected abstract void Activate (T source);

		protected abstract BindableProperty IsEnabledProperty
		{
			get;
		}

		protected abstract BindableProperty CommandProperty
		{
			get;
		}

		protected abstract BindableProperty CommandParameterProperty
		{
			get;
		}
	}
}