Add TestWindowsSymlinkFactory

tests/Tgstation.Server.Host.Tests/IO/TestWindowsSymlinkFactory.cs

@@ -0,0 +1,57 @@
+using Microsoft.VisualStudio.TestTools.UnitTesting;
+using System;
+using System.ComponentModel;
+using System.IO;
+using System.Runtime.InteropServices;
+using System.Threading.Tasks;
+
+namespace Tgstation.Server.Host.IO.Tests
+{
+	[TestClass]
+	public sealed class TestWindowsSymlinkFactory
+	{
+		[TestMethod]
+		public async Task TestWorks()
+		{
+			if (!RuntimeInformation.IsOSPlatform(OSPlatform.Windows))
+				Assert.Inconclusive("Windows only test");
+
+			var factory = new WindowsSymlinkFactory();
+
+			const string Text = "Hello world";
+			string f2 = null;
+			var f1 = Path.GetTempFileName();
+			try
+			{
+				f2 = f1 + ".linked";
+				File.WriteAllText(f1, Text);
+
+				await Assert.ThrowsExceptionAsync<ArgumentNullException>(() => factory.CreateSymbolicLink(null, null, default)).ConfigureAwait(false);
+				await Assert.ThrowsExceptionAsync<ArgumentNullException>(() => factory.CreateSymbolicLink(f1, null, default)).ConfigureAwait(false);
+
+				await factory.CreateSymbolicLink(f1, f2, default).ConfigureAwait(false);
+
+				var f2Contents = File.ReadAllText(f2);
+				Assert.AreEqual(Text, f2Contents);
+			}
+			finally
+			{
+				File.Delete(f2);
+				File.Delete(f1);
+			}
+		}
+
+		[TestMethod]
+		public async Task TestFailsProperly()
+		{
+			if (!RuntimeInformation.IsOSPlatform(OSPlatform.Windows))
+				Assert.Inconclusive("Windows only test");
+
+			var factory = new WindowsSymlinkFactory();
+
+			const string BadPath = "C:/?><:{ }";
+
+			await Assert.ThrowsExceptionAsync<Win32Exception>(() => factory.CreateSymbolicLink(BadPath, BadPath, default)).ConfigureAwait(false);
+		}
+	}
+}