Seal the ruleset creation methods and let abstract method take their place

Also makes `CreatePlayerRuleset()` and `CreateRulesetForSkinProvider()` not-null to avoid unwanted behaviour with their derivers

osu.Game.Rulesets.Catch.Tests/CatchSkinnableTestScene.cs

@@ -16,6 +16,6 @@ namespace osu.Game.Rulesets.Catch.Tests
             typeof(CatchLegacySkinTransformer),
         };
 
-        protected override Ruleset CreateRuleset() => new CatchRuleset();
+        protected override Ruleset CreateRulesetForSkinProvider() => new CatchRuleset();
     }
 }

osu.Game.Rulesets.Catch.Tests/Mods/TestSceneCatchModPerfect.cs

@@ -13,6 +13,8 @@ namespace osu.Game.Rulesets.Catch.Tests.Mods
 {
     public class TestSceneCatchModPerfect : ModPerfectTestScene
     {
+        protected override Ruleset CreatePlayerRuleset() => new CatchRuleset();
+
         public TestSceneCatchModPerfect()
             : base(new CatchModPerfect())
         {
@@ -50,7 +52,5 @@ namespace osu.Game.Rulesets.Catch.Tests.Mods
         // We only care about testing misses, hits are tested via JuiceStream
         [TestCase(true)]
         public void TestTinyDroplet(bool shouldMiss) => CreateHitObjectTest(new HitObjectTestData(new TinyDroplet { StartTime = 1000 }), shouldMiss);
-
-        protected override Ruleset CreateRuleset() => new CatchRuleset();
     }
 }

osu.Game.Rulesets.Catch.Tests/TestSceneCatchPlayer.cs

@@ -16,6 +16,6 @@ namespace osu.Game.Rulesets.Catch.Tests
             typeof(CatchRuleset),
         };
 
-        protected override Ruleset CreateRuleset() => new CatchRuleset();
+        protected override Ruleset CreatePlayerRuleset() => new CatchRuleset();
     }
 }

osu.Game.Rulesets.Mania.Tests/Mods/TestSceneManiaModPerfect.cs

@@ -10,6 +10,8 @@ namespace osu.Game.Rulesets.Mania.Tests.Mods
 {
     public class TestSceneManiaModPerfect : ModPerfectTestScene
     {
+        protected override Ruleset CreatePlayerRuleset() => new ManiaRuleset();
+
         public TestSceneManiaModPerfect()
             : base(new ManiaModPerfect())
         {
@@ -22,7 +24,5 @@ namespace osu.Game.Rulesets.Mania.Tests.Mods
         [TestCase(false)]
         [TestCase(true)]
         public void TestHoldNote(bool shouldMiss) => CreateHitObjectTest(new HitObjectTestData(new HoldNote { StartTime = 1000, EndTime = 3000 }), shouldMiss);
-
-        protected override Ruleset CreateRuleset() => new ManiaRuleset();
     }
 }

osu.Game.Rulesets.Mania.Tests/Skinning/ManiaSkinnableTestScene.cs

@@ -34,6 +34,8 @@ namespace osu.Game.Rulesets.Mania.Tests.Skinning
             typeof(ManiaSettingsSubsection)
         };
 
+        protected override Ruleset CreateRulesetForSkinProvider() => new ManiaRuleset();
+
         protected ManiaSkinnableTestScene()
         {
             scrollingInfo.Direction.Value = ScrollingDirection.Down;
@@ -58,8 +60,6 @@ namespace osu.Game.Rulesets.Mania.Tests.Skinning
             AddStep("change direction to up", () => scrollingInfo.Direction.Value = ScrollingDirection.Up);
         }
 
-        protected override Ruleset CreateRuleset() => new ManiaRuleset();
-
         private class TestScrollingInfo : IScrollingInfo
         {
             public readonly Bindable<ScrollingDirection> Direction = new Bindable<ScrollingDirection>();

osu.Game.Rulesets.Mania.Tests/TestSceneManiaPlayer.cs

@@ -14,6 +14,6 @@ namespace osu.Game.Rulesets.Mania.Tests
             typeof(ManiaRuleset),
         };
 
-        protected override Ruleset CreateRuleset() => new ManiaRuleset();
+        protected override Ruleset CreatePlayerRuleset() => new ManiaRuleset();
     }
 }

osu.Game.Rulesets.Osu.Tests/Mods/TestSceneOsuModDifficultyAdjust.cs

@@ -15,6 +15,8 @@ namespace osu.Game.Rulesets.Osu.Tests.Mods
 {
     public class TestSceneOsuModDifficultyAdjust : ModTestScene
     {
+        protected override Ruleset CreatePlayerRuleset() => new OsuRuleset();
+
         [Test]
         public void TestNoAdjustment() => CreateModTest(new ModTestData
         {
@@ -77,7 +79,5 @@ namespace osu.Game.Rulesets.Osu.Tests.Mods
         {
             return Player.ScoreProcessor.JudgedHits >= 2;
         }
-
-        protected override Ruleset CreateRuleset() => new OsuRuleset();
     }
 }

osu.Game.Rulesets.Osu.Tests/Mods/TestSceneOsuModDoubleTime.cs

@@ -10,6 +10,8 @@ namespace osu.Game.Rulesets.Osu.Tests.Mods
 {
     public class TestSceneOsuModDoubleTime : ModTestScene
     {
+        protected override Ruleset CreatePlayerRuleset() => new OsuRuleset();
+
         [TestCase(0.5)]
         [TestCase(1.01)]
         [TestCase(1.5)]
@@ -26,7 +28,5 @@ namespace osu.Game.Rulesets.Osu.Tests.Mods
                                       Precision.AlmostEquals(Player.GameplayClockContainer.GameplayClock.Rate, mod.SpeedChange.Value)
             });
         }
-
-        protected override Ruleset CreateRuleset() => new OsuRuleset();
     }
 }

osu.Game.Rulesets.Osu.Tests/Mods/TestSceneOsuModPerfect.cs

@@ -13,6 +13,8 @@ namespace osu.Game.Rulesets.Osu.Tests.Mods
 {
     public class TestSceneOsuModPerfect : ModPerfectTestScene
     {
+        protected override Ruleset CreatePlayerRuleset() => new OsuRuleset();
+
         public TestSceneOsuModPerfect()
             : base(new OsuModPerfect())
         {
@@ -48,7 +50,5 @@ namespace osu.Game.Rulesets.Osu.Tests.Mods
 
             CreateHitObjectTest(new HitObjectTestData(spinner), shouldMiss);
         }
-
-        protected override Ruleset CreateRuleset() => new OsuRuleset();
     }
 }

osu.Game.Rulesets.Osu.Tests/OsuSkinnableTestScene.cs

@@ -16,6 +16,6 @@ namespace osu.Game.Rulesets.Osu.Tests
             typeof(OsuLegacySkinTransformer),
         };
 
-        protected override Ruleset CreateRuleset() => new OsuRuleset();
+        protected override Ruleset CreateRulesetForSkinProvider() => new OsuRuleset();
     }
 }

osu.Game.Rulesets.Osu.Tests/TestSceneMissHitWindowJudgements.cs

@@ -19,6 +19,8 @@ namespace osu.Game.Rulesets.Osu.Tests
 {
     public class TestSceneMissHitWindowJudgements : ModTestScene
     {
+        protected override Ruleset CreatePlayerRuleset() => new OsuRuleset();
+
         [Test]
         public void TestMissViaEarlyHit()
         {
@@ -61,8 +63,6 @@ namespace osu.Game.Rulesets.Osu.Tests
             });
         }
 
-        protected override Ruleset CreateRuleset() => new OsuRuleset();
-
         private class TestAutoMod : OsuModAutoplay
         {
             public override Score CreateReplayScore(IBeatmap beatmap) => new Score

osu.Game.Rulesets.Osu.Tests/TestSceneOsuPlayer.cs

@@ -16,6 +16,6 @@ namespace osu.Game.Rulesets.Osu.Tests
             typeof(OsuRuleset),
         };
 
-        protected override Ruleset CreateRuleset() => new OsuRuleset();
+        protected override Ruleset CreatePlayerRuleset() => new OsuRuleset();
     }
 }

osu.Game.Rulesets.Taiko.Tests/Mods/TestSceneTaikoModPerfect.cs

@@ -12,6 +12,8 @@ namespace osu.Game.Rulesets.Taiko.Tests.Mods
 {
     public class TestSceneTaikoModPerfect : ModPerfectTestScene
     {
+        protected override Ruleset CreatePlayerRuleset() => new TestTaikoRuleset();
+
         public TestSceneTaikoModPerfect()
             : base(new TaikoModPerfect())
         {
@@ -29,8 +31,6 @@ namespace osu.Game.Rulesets.Taiko.Tests.Mods
         [TestCase(true)]
         public void TestSwell(bool shouldMiss) => CreateHitObjectTest(new HitObjectTestData(new Swell { StartTime = 1000, EndTime = 3000 }), shouldMiss);
 
-        protected override Ruleset CreateRuleset() => new TestTaikoRuleset();
-
         private class TestTaikoRuleset : TaikoRuleset
         {
             public override HealthProcessor CreateHealthProcessor(double drainStartTime) => new TestTaikoHealthProcessor();

osu.Game.Rulesets.Taiko.Tests/TaikoSkinnableTestScene.cs

@@ -16,6 +16,6 @@ namespace osu.Game.Rulesets.Taiko.Tests
             typeof(TaikoLegacySkinTransformer),
         };
 
-        protected override Ruleset CreateRuleset() => new TaikoRuleset();
+        protected override Ruleset CreateRulesetForSkinProvider() => new TaikoRuleset();
     }
 }

osu.Game.Rulesets.Taiko.Tests/TestSceneTaikoPlayer.cs

@@ -14,6 +14,6 @@ namespace osu.Game.Rulesets.Taiko.Tests
             typeof(TaikoRuleset)
         };
 
-        protected override Ruleset CreateRuleset() => new TaikoRuleset();
+        protected override Ruleset CreatePlayerRuleset() => new TaikoRuleset();
     }
 }

osu.Game.Tests/Visual/Gameplay/TestPlayerTestScene.cs

@@ -11,6 +11,6 @@ namespace osu.Game.Tests.Visual.Gameplay
     /// </summary>
     public abstract class TestPlayerTestScene : PlayerTestScene
     {
-        protected override Ruleset CreateRuleset() => new OsuRuleset();
+        protected override Ruleset CreatePlayerRuleset() => new OsuRuleset();
     }
 }

osu.Game/Tests/Visual/PlayerTestScene.cs

@@ -3,6 +3,7 @@
 
 using System;
 using System.Linq;
+using JetBrains.Annotations;
 using osu.Framework.Allocation;
 using osu.Framework.Extensions.IEnumerableExtensions;
 using osu.Framework.Testing;
@@ -23,6 +24,22 @@ namespace osu.Game.Tests.Visual
 
         protected OsuConfigManager LocalConfig;
 
+        /// <summary>
+        /// Creates the ruleset for setting up the <see cref="Player"/> component.
+        /// </summary>
+        [NotNull]
+        protected abstract Ruleset CreatePlayerRuleset();
+
+        protected sealed override Ruleset CreateRuleset() => CreatePlayerRuleset();
+
+        [NotNull]
+        private readonly Ruleset ruleset;
+
+        protected PlayerTestScene()
+        {
+            ruleset = CreatePlayerRuleset();
+        }
+
         [BackgroundDependencyLoader]
         private void load()
         {
@@ -46,7 +63,7 @@ namespace osu.Game.Tests.Visual
 
             action?.Invoke();
 
-            AddStep(CreateRuleset().RulesetInfo.Name, LoadPlayer);
+            AddStep(ruleset.Description, LoadPlayer);
             AddUntilStep("player loaded", () => Player.IsLoaded && Player.Alpha == 1);
         }
 
@@ -56,28 +73,27 @@ namespace osu.Game.Tests.Visual
 
         protected void LoadPlayer()
         {
-            var beatmap = CreateBeatmap(Ruleset.Value);
+            var beatmap = CreateBeatmap(ruleset.RulesetInfo);
 
             Beatmap.Value = CreateWorkingBeatmap(beatmap);
+            Ruleset.Value = ruleset.RulesetInfo;
             SelectedMods.Value = Array.Empty<Mod>();
 
-            var rulesetInstance = Ruleset.Value.CreateInstance();
-
             if (!AllowFail)
             {
-                var noFailMod = rulesetInstance.GetAllMods().FirstOrDefault(m => m is ModNoFail);
+                var noFailMod = ruleset.GetAllMods().FirstOrDefault(m => m is ModNoFail);
                 if (noFailMod != null)
                     SelectedMods.Value = new[] { noFailMod };
             }
 
             if (Autoplay)
             {
-                var mod = rulesetInstance.GetAutoplayMod();
+                var mod = ruleset.GetAutoplayMod();
                 if (mod != null)
                     SelectedMods.Value = SelectedMods.Value.Concat(mod.Yield()).ToArray();
             }
 
-            Player = CreatePlayer(rulesetInstance);
+            Player = CreatePlayer(ruleset);
             LoadScreen(Player);
         }
 

osu.Game/Tests/Visual/SkinnableTestScene.cs

@@ -4,6 +4,7 @@
 using System;
 using System.Collections.Generic;
 using System.Text.RegularExpressions;
+using JetBrains.Annotations;
 using osu.Framework.Allocation;
 using osu.Framework.Audio;
 using osu.Framework.Graphics;
@@ -13,6 +14,7 @@ using osu.Framework.Graphics.Textures;
 using osu.Framework.IO.Stores;
 using osu.Game.Beatmaps;
 using osu.Game.Graphics.Sprites;
+using osu.Game.Rulesets;
 using osu.Game.Skinning;
 using osuTK;
 using osuTK.Graphics;
@@ -26,16 +28,17 @@ namespace osu.Game.Tests.Visual
         private Skin specialSkin;
         private Skin oldSkin;
 
+        /// <summary>
+        /// Creates the ruleset for adding the ruleset-specific skin transforming component.
+        /// </summary>
+        [NotNull]
+        protected abstract Ruleset CreateRulesetForSkinProvider();
+
+        protected sealed override Ruleset CreateRuleset() => CreateRulesetForSkinProvider();
+
         protected SkinnableTestScene()
             : base(2, 3)
         {
-            // avoid running silently incorrectly.
-            if (CreateRuleset() == null)
-            {
-                throw new InvalidOperationException(
-                    $"No ruleset provided, override {nameof(CreateRuleset)} to the ruleset belonging to the skinnable content."
-                    + "This is required to add the legacy skin transformer for the content to behave as expected.");
-            }
         }
 
         [BackgroundDependencyLoader]
@@ -110,7 +113,7 @@ namespace osu.Game.Tests.Visual
                         {
                             new OutlineBox { Alpha = autoSize ? 1 : 0 },
                             mainProvider.WithChild(
-                                new SkinProvidingContainer(Ruleset.Value.CreateInstance().CreateLegacySkinProvider(mainProvider, beatmap))
+                                new SkinProvidingContainer(CreateRulesetForSkinProvider().CreateLegacySkinProvider(mainProvider, beatmap))
                                 {
                                     Child = created,
                                     RelativeSizeAxes = !autoSize ? Axes.Both : Axes.None,