Add BUI ctor tests (#31463)

5 lines of eaten iocmanager.injectdependencies led to this.

Content.IntegrationTests/Tests/UserInterface/UiControlTest.cs

@@ -0,0 +1,58 @@
+using System.Linq;
+using Content.Client.Chat.UI;
+using Content.Client.LateJoin;
+using Robust.Client.UserInterface.CustomControls;
+using Robust.Shared.ContentPack;
+using Robust.Shared.IoC;
+using Robust.Shared.Reflection;
+
+namespace Content.IntegrationTests.Tests.UserInterface;
+
+[TestFixture]
+public sealed class UiControlTest
+{
+    // You should not be adding to this.
+    private Type[] _ignored = new Type[]
+    {
+        typeof(EmotesMenu),
+        typeof(LateJoinGui),
+    };
+
+    /// <summary>
+    /// Tests that all windows can be instantiated successfully.
+    /// </summary>
+    [Test]
+    public async Task TestWindows()
+    {
+        var pair = await PoolManager.GetServerClient(new PoolSettings()
+        {
+            Connected = true,
+        });
+        var activator = pair.Client.ResolveDependency<IDynamicTypeFactory>();
+        var refManager = pair.Client.ResolveDependency<IReflectionManager>();
+        var loader = pair.Client.ResolveDependency<IModLoader>();
+
+        await pair.Client.WaitAssertion(() =>
+        {
+            foreach (var type in refManager.GetAllChildren(typeof(BaseWindow)))
+            {
+                if (type.IsAbstract || _ignored.Contains(type))
+                    continue;
+
+                if (!loader.IsContentType(type))
+                    continue;
+
+                // If it has no empty ctor then skip it instead of figuring out what args it needs.
+                var ctor = type.GetConstructor(Type.EmptyTypes);
+
+                if (ctor == null)
+                    continue;
+
+                // Don't inject because the control themselves have to do it.
+                activator.CreateInstance(type, oneOff: true, inject: false);
+            }
+        });
+
+        await pair.CleanReturnAsync();
+    }
+}