Add TestAsyncDelayer

tests/Tgstation.Server.Host.Tests/Core/TestAsyncDelayer.cs

@@ -0,0 +1,32 @@
+using Microsoft.VisualStudio.TestTools.UnitTesting;
+using System;
+using System.Threading;
+using System.Threading.Tasks;
+
+namespace Tgstation.Server.Host.Core.Tests
+{
+	[TestClass]
+	public sealed class TestAsyncDelayer
+	{
+		[TestMethod]
+		public async Task TestDelay()
+		{
+			var delayer = new AsyncDelayer();
+			var startDelay = delayer.Delay(TimeSpan.FromSeconds(1), default);
+			var checkDelay = Task.Delay(TimeSpan.FromSeconds(1) - TimeSpan.FromMilliseconds(10), default);
+			await startDelay.ConfigureAwait(false);
+			Assert.IsTrue(checkDelay.IsCompleted);
+		}
+
+		[TestMethod]
+		public async Task TestCancel()
+		{
+			var delayer = new AsyncDelayer();
+			using (var cts = new CancellationTokenSource())
+			{
+				cts.Cancel();
+				await Assert.ThrowsExceptionAsync<TaskCanceledException>(() => delayer.Delay(TimeSpan.FromSeconds(1), cts.Token)).ConfigureAwait(false);
+			}
+		}
+	}
+}