Avalonia/tests/Avalonia.Base.UnitTests/Data/Core/ExpressionObserverTests_Negation.cs

using System;
using System.Reactive.Linq;
using System.Threading.Tasks;
using Avalonia.Data;
using Avalonia.Data.Core;
using Avalonia.Markup.Parsers;
using Xunit;

namespace Avalonia.Base.UnitTests.Data.Core
{
    public class ExpressionObserverTests_Negation
    {
        [Fact]
        public async Task Should_Negate_Boolean_Value()
        {
            var data = new { Foo = true };
            var target = ExpressionObserver.Create(data, o => !o.Foo);
            var result = await target.Take(1);

            Assert.False((bool)result);

            GC.KeepAlive(data);
        }

        [Fact]
        public void Can_SetValue_For_Valid_Value()
        {
            var data = new Test { Foo = true };
            var target = ExpressionObserver.Create(data, o => !o.Foo);
            target.Subscribe(_ => { });

            Assert.True(target.SetValue(true));

            Assert.False(data.Foo);
        }

        private class Test
        {
            public bool Foo { get; set; }
        }
    }
}