Move SkinnableTestScene into using the global CreateRuleset method

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

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

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

@@ -34,8 +34,6 @@ namespace osu.Game.Rulesets.Mania.Tests.Skinning
             typeof(ManiaSettingsSubsection)
         };
 
-        protected override Ruleset CreateRulesetForSkinProvider() => new ManiaRuleset();
-
         protected ManiaSkinnableTestScene()
         {
             scrollingInfo.Direction.Value = ScrollingDirection.Down;
@@ -60,6 +58,8 @@ 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.Osu.Tests/OsuSkinnableTestScene.cs

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

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

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

osu.Game/Tests/Visual/SkinnableTestScene.cs

@@ -13,7 +13,6 @@ 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;
@@ -30,10 +29,14 @@ namespace osu.Game.Tests.Visual
         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.");
+            }
         }
-
-        // Required to be part of the per-ruleset implementation to construct the newer version of the Ruleset.
-        protected abstract Ruleset CreateRulesetForSkinProvider();
 
         [BackgroundDependencyLoader]
         private void load(AudioManager audio, SkinManager skinManager)
@@ -107,7 +110,7 @@ namespace osu.Game.Tests.Visual
                         {
                             new OutlineBox { Alpha = autoSize ? 1 : 0 },
                             mainProvider.WithChild(
-                                new SkinProvidingContainer(CreateRulesetForSkinProvider().CreateLegacySkinProvider(mainProvider, beatmap))
+                                new SkinProvidingContainer(Ruleset.Value.CreateInstance().CreateLegacySkinProvider(mainProvider, beatmap))
                                 {
                                     Child = created,
                                     RelativeSizeAxes = !autoSize ? Axes.Both : Axes.None,