Add regression test for the pattern of using DHO proxy in LifetimeManagementContainer

osu.Game.Tests/Gameplay/TestSceneProxyContainer.cs

@@ -0,0 +1,85 @@
+// 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.Collections.Generic;
+using NUnit.Framework;
+using osu.Framework.Graphics;
+using osu.Framework.Graphics.Containers;
+using osu.Framework.Testing;
+using osu.Framework.Timing;
+using osu.Game.Rulesets.Objects;
+using osu.Game.Rulesets.Objects.Drawables;
+using osu.Game.Rulesets.UI;
+using osu.Game.Tests.Visual;
+
+namespace osu.Game.Tests.Gameplay
+{
+    [HeadlessTest]
+    public class TestSceneProxyContainer : OsuTestScene
+    {
+        private HitObjectContainer hitObjectContainer;
+        private ProxyContainer proxyContainer;
+        private readonly ManualClock clock = new ManualClock();
+
+        [SetUp]
+        public void SetUp() => Schedule(() =>
+        {
+            Child = new Container
+            {
+                Children = new Drawable[]
+                {
+                    hitObjectContainer = new HitObjectContainer(),
+                    proxyContainer = new ProxyContainer()
+                },
+                Clock = new FramedClock(clock)
+            };
+            clock.CurrentTime = 0;
+        });
+
+        [Test]
+        public void TestProxyLifetimeManagement()
+        {
+            AddStep("Add proxy drawables", () =>
+            {
+                addProxy(new TestDrawableHitObject(1000));
+                addProxy(new TestDrawableHitObject(3000));
+                addProxy(new TestDrawableHitObject(5000));
+            });
+
+            AddStep($"time = 1000", () => clock.CurrentTime = 1000);
+            AddAssert("One proxy is alive", () => proxyContainer.AliveChildren.Count == 1);
+            AddStep($"time = 5000", () => clock.CurrentTime = 5000);
+            AddAssert("One proxy is alive", () => proxyContainer.AliveChildren.Count == 1);
+            AddStep($"time = 6000", () => clock.CurrentTime = 6000);
+            AddAssert("No proxy is alive", () => proxyContainer.AliveChildren.Count == 0);
+        }
+
+        private void addProxy(DrawableHitObject drawableHitObject)
+        {
+            hitObjectContainer.Add(drawableHitObject);
+            proxyContainer.AddProxy(drawableHitObject);
+        }
+
+        private class ProxyContainer : LifetimeManagementContainer
+        {
+            public IReadOnlyList<Drawable> AliveChildren => AliveInternalChildren;
+
+            public void AddProxy(Drawable d) => AddInternal(d.CreateProxy());
+        }
+
+        private class TestDrawableHitObject : DrawableHitObject
+        {
+            protected override double InitialLifetimeOffset => 100;
+
+            public TestDrawableHitObject(double startTime)
+                : base(new HitObject { StartTime = startTime })
+            {
+            }
+
+            protected override void UpdateInitialTransforms()
+            {
+                LifetimeEnd = LifetimeStart + 500;
+            }
+        }
+    }
+}