Add failing test coverage of fast streams not working in editor

osu.Game.Rulesets.Osu.Tests/Editor/TestSceneEditorAutoplayFastStreams.cs

@@ -0,0 +1,51 @@
+// 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.Testing;
+using osu.Game.Beatmaps;
+using osu.Game.Rulesets.Osu.Objects;
+using osu.Game.Rulesets.Osu.Objects.Drawables;
+using osu.Game.Tests.Beatmaps;
+using osu.Game.Tests.Visual;
+
+namespace osu.Game.Rulesets.Osu.Tests.Editor
+{
+    /// <summary>
+    /// This test covers autoplay working correctly in the editor on fast streams.
+    /// Might seem like a weird test, but frame stability being toggled can cause autoplay to operation incorrectly.
+    /// This is clearly a bug with the autoplay algorithm, but is worked around at an editor level for now.
+    /// </summary>
+    public partial class TestSceneEditorAutoplayFastStreams : EditorTestScene
+    {
+        protected override IBeatmap CreateBeatmap(RulesetInfo ruleset)
+        {
+            var testBeatmap = new TestBeatmap(ruleset, false);
+            testBeatmap.HitObjects.AddRange(new[]
+            {
+                new HitCircle { StartTime = 500 },
+                new HitCircle { StartTime = 530 },
+                new HitCircle { StartTime = 560 },
+                new HitCircle { StartTime = 590 },
+                new HitCircle { StartTime = 620 },
+            });
+
+            return testBeatmap;
+        }
+
+        protected override Ruleset CreateEditorRuleset() => new OsuRuleset();
+
+        [Test]
+        public void TestAllHit()
+        {
+            AddStep("start playback", () => EditorClock.Start());
+            AddUntilStep("wait for all hit", () =>
+            {
+                DrawableHitCircle[] hitCircles = Editor.ChildrenOfType<DrawableHitCircle>().OrderBy(s => s.HitObject.StartTime).ToArray();
+
+                return hitCircles.Length == 5 && hitCircles.All(h => h.IsHit);
+            });
+        }
+    }
+}