Fix build and add tests

Template.Tests/StartupTest.cs

@@ -0,0 +1,40 @@
+using NUnit.Framework;
+using Robust.Client;
+using Robust.Shared.IoC;
+using Robust.UnitTesting;
+using Template.Game;
+
+namespace Template.Tests;
+
+[TestFixture]
+public sealed class StartupTest : RobustIntegrationTest
+{
+    [Test]
+    public async Task GameStartsSingleplayer()
+    {
+        var client = StartClient(new ClientIntegrationOptions
+        {
+            ContentStart = true,
+            ContentAssemblies = [typeof(EntryPoint).Assembly],
+            Options = new GameControllerOptions
+            {
+                ContentModulePrefix = "Template.",
+                ContentBuildDirectory = "Template.Game",
+                LoadConfigAndUserData = false,
+                LoadContentResources = false,
+            },
+        });
+
+        await client.WaitIdleAsync();
+
+        Assert.That(client.IsAlive, Is.True);
+        Assert.That(client.UnhandledException, Is.Null);
+
+        await client.WaitAssertion(() =>
+        {
+            var baseClient = IoCManager.Resolve<IBaseClient>();
+
+            Assert.That(baseClient.RunLevel, Is.EqualTo(ClientRunLevel.SinglePlayerGame));
+        });
+    }
+}