Add attribute to mark visual tests that should only run via nUnit

osu.Framework.Tests/Visual/Containers/TestSceneCompositeMutability.cs osu.Framework.Tests/Containers/TestSceneCompositeMutability.cs

···
 using NUnit.Framework;
 using osu.Framework.Allocation;
 using osu.Framework.Graphics;
-using osu.Framework.Graphics.Containers;
 using osu.Framework.Graphics.Shapes;
+using osu.Framework.Testing;
+using osu.Framework.Tests.Visual;
 
-namespace osu.Framework.Tests.Visual.Containers
+namespace osu.Framework.Tests.Containers
 {
+    [HeadlessTest]
     public class TestSceneCompositeMutability : FrameworkTestScene
     {
         [TestCase(TestThread.External, false)]
···
             }
         }
 
-        private class BlockableLoadContainer : Container
+        private class BlockableLoadContainer : Framework.Graphics.Containers.Container
         {
             /// <summary>
             /// Allows continuation to a point in the <see cref="LoadState.Loading"/> state which invokes <see cref="OnLoading"/>.

osu.Framework.Tests/Visual/Containers/TestSceneContainerState.cs osu.Framework.Tests/Containers/TestSceneContainerState.cs

···
 using osu.Framework.Graphics.Containers;
 using osu.Framework.Graphics.Shapes;
 using osu.Framework.Graphics.Sprites;
+using osu.Framework.Testing;
+using osu.Framework.Tests.Visual;
 
-namespace osu.Framework.Tests.Visual.Containers
+namespace osu.Framework.Tests.Containers
 {
     [System.ComponentModel.Description("ensure valid container state in various scenarios")]
+    [HeadlessTest]
     public class TestSceneContainerState : FrameworkTestScene
     {
         /// <summary>

osu.Framework.Tests/Visual/Containers/TestSceneLoadComponentAsync.cs osu.Framework.Tests/Containers/TestSceneLoadComponentAsync.cs

···
 using osu.Framework.Graphics;
 using osu.Framework.Graphics.Containers;
 using osu.Framework.Testing;
+using osu.Framework.Tests.Visual;
 
-namespace osu.Framework.Tests.Visual.Containers
+namespace osu.Framework.Tests.Containers
 {
+    [HeadlessTest]
     public class TestSceneLoadComponentAsync : FrameworkTestScene
     {
         private AsyncChildLoadingComposite composite;

osu.Framework.Tests/Visual/Sprites/TestSceneSpriteTextPresence.cs osu.Framework.Tests/Sprites/TestSceneSpriteTextPresence.cs

···
 using osu.Framework.Graphics.Shapes;
 using osu.Framework.Graphics.Sprites;
 using osu.Framework.MathUtils;
+using osu.Framework.Testing;
+using osu.Framework.Tests.Visual;
 using osuTK.Graphics;
 
-namespace osu.Framework.Tests.Visual.Sprites
+namespace osu.Framework.Tests.Sprites
 {
+    [HeadlessTest]
     public class TestSceneSpriteTextPresence : FrameworkTestScene
     {
         /// <summary>

osu.Framework/Testing/HeadlessTestAttribute.cs

···
+// Copyright (c) ppy Pty Ltd <[e-mail]>. Licensed under the MIT Licence.
+// See the LICENCE file in the repository root for full licence text.
+
+using System;
+using JetBrains.Annotations;
+
+namespace osu.Framework.Testing
+{
+    /// <summary>
+    /// Denotes a "visual" test which should only be run in a headless context.
+    /// This will stop the test from showing up in a <see cref="TestBrowser"/>.
+    /// </summary>
+    [AttributeUsage(AttributeTargets.Class)]
+    [MeansImplicitUse]
+    public class HeadlessTestAttribute : Attribute
+    {
+    }
+}

osu.Framework/Testing/TestBrowser.cs

···
             //we want to build the lists here because we're interested in the assembly we were *created* on.
             foreach (Assembly asm in assemblies.ToList())
             {
-                var tests = asm.GetLoadableTypes().Where(t => t.IsSubclassOf(typeof(TestScene)) && !t.IsAbstract && t.IsPublic).ToList();
+                var tests = asm.GetLoadableTypes().Where(isValidVisualTest).ToList();
 
                 if (!tests.Any())
                 {
···
 
             TestTypes.Sort((a, b) => string.Compare(a.Name, b.Name, StringComparison.Ordinal));
         }
+
+        private bool isValidVisualTest(Type t) => t.IsSubclassOf(typeof(TestScene)) && !t.IsAbstract && t.IsPublic && !t.GetCustomAttributes<HeadlessTestAttribute>().Any();
 
         private void updateList(ValueChangedEvent<Assembly> args)
         {