Add sandbox test (#10767)

Content.IntegrationTests/Tests/Utility/SandboxTest.cs

@@ -0,0 +1,16 @@
+using System.Threading.Tasks;
+using NUnit.Framework;
+
+namespace Content.IntegrationTests.Tests.Utility;
+
+public sealed class SandboxTest
+{
+    [Test]
+    public async Task Test()
+    {
+        await using var pairTracker = await PoolManager.GetServerClient(new PoolSettings{NoServer = true});
+        var client = pairTracker.Pair.Client;
+        await client.CheckSandboxed(typeof(Client.Entry.EntryPoint).Assembly);
+        await pairTracker.CleanReturnAsync();
+    }
+}