Add CancellationToken.WaitUntilCanceled

src/UniTask.NetCoreTests/CancellationTokenTest.cs

@@ -0,0 +1,51 @@
+using Cysharp.Threading.Tasks;
+using FluentAssertions;
+using System;
+using System.Collections.Generic;
+using System.Linq;
+using System.Text;
+using System.Threading;
+using System.Threading.Channels;
+using Cysharp.Threading.Tasks.Linq;
+using System.Threading.Tasks;
+using Xunit;
+
+namespace NetCoreTests
+{
+    public class CancellationTokenTest
+    {
+        [Fact]
+        public async Task WaitUntilCanceled()
+        {
+            var cts = new CancellationTokenSource();
+
+            cts.CancelAfter(TimeSpan.FromSeconds(1.5));
+
+            var now = DateTime.UtcNow;
+
+            await cts.Token.WaitUntilCanceled();
+
+            var elapsed = DateTime.UtcNow - now;
+
+            elapsed.Should().BeGreaterThan(TimeSpan.FromSeconds(1));
+        }
+
+        [Fact]
+        public void AlreadyCanceled()
+        {
+            var cts = new CancellationTokenSource();
+
+            cts.Cancel();
+
+            cts.Token.WaitUntilCanceled().GetAwaiter().IsCompleted.Should().BeTrue();
+        }
+
+        [Fact]
+        public void None()
+        {
+            CancellationToken.None.WaitUntilCanceled().GetAwaiter().IsCompleted.Should().BeTrue();
+        }
+    }
+
+
+}