Add basic test coverage

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

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+// Copyright (c) ppy Pty Ltd <contact@ppy.sh>. Licensed under the MIT Licence.
+// See the LICENCE file in the repository root for full licence text.
+
+using System.Linq;
+using NUnit.Framework;
+using osu.Framework.Allocation;
+using osu.Framework.Graphics;
+using osu.Framework.Testing;
+using osu.Game.Rulesets;
+using osu.Game.Rulesets.Osu;
+using osu.Game.Skinning;
+using osu.Game.Storyboards;
+using osu.Game.Storyboards.Drawables;
+using osuTK;
+
+namespace osu.Game.Tests.Visual.Gameplay
+{
+    public class TestSceneDrawableStoryboardSprite : SkinnableTestScene
+    {
+        protected override Ruleset CreateRulesetForSkinProvider() => new OsuRuleset();
+
+        [Cached]
+        private Storyboard storyboard { get; set; } = new Storyboard();
+
+        [Test]
+        public void TestSkinSpriteDisallowedByDefault()
+        {
+            const string lookup_name = "hitcircleoverlay";
+
+            AddStep("allow skin lookup", () => storyboard.UseSkinSprites = false);
+
+            AddStep("create sprites", () => SetContents(
+                () => createSprite(lookup_name, Anchor.TopLeft, Vector2.Zero)));
+
+            assertSpritesFromSkin(false);
+        }
+
+        [Test]
+        public void TestAllowLookupFromSkin()
+        {
+            const string lookup_name = "hitcircleoverlay";
+
+            AddStep("allow skin lookup", () => storyboard.UseSkinSprites = true);
+
+            AddStep("create sprites", () => SetContents(
+                () => createSprite(lookup_name, Anchor.Centre, Vector2.Zero)));
+
+            assertSpritesFromSkin(true);
+        }
+
+        private DrawableStoryboardSprite createSprite(string lookupName, Anchor origin, Vector2 initialPosition)
+            => new DrawableStoryboardSprite(
+                new StoryboardSprite(lookupName, origin, initialPosition)
+            ).With(s =>
+            {
+                s.LifetimeStart = double.MinValue;
+                s.LifetimeEnd = double.MaxValue;
+            });
+
+        private void assertSpritesFromSkin(bool fromSkin) =>
+            AddAssert($"sprites are {(fromSkin ? "from skin" : "from storyboard")}",
+                () => this.ChildrenOfType<DrawableStoryboardSprite>()
+                          .All(sprite => sprite.ChildrenOfType<SkinnableSprite>().Any() == fromSkin));
+    }
+}