Add test coverage of realm subscription scenarios

osu.Game.Tests/Database/RealmSubscriptionRegistrationTests.cs

@@ -0,0 +1,138 @@
+// 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;
+using System.Collections.Generic;
+using System.Linq;
+using NUnit.Framework;
+using osu.Framework.Allocation;
+using osu.Game.Beatmaps;
+using osu.Game.Rulesets;
+using osu.Game.Tests.Resources;
+using Realms;
+
+#nullable enable
+
+namespace osu.Game.Tests.Database
+{
+    [TestFixture]
+    public class RealmSubscriptionRegistrationTests : RealmTest
+    {
+        [Test]
+        public void TestSubscriptionWithContextLoss()
+        {
+            IEnumerable<BeatmapSetInfo>? resolvedItems = null;
+            ChangeSet? lastChanges = null;
+
+            RunTestWithRealm((realmFactory, _) =>
+            {
+                realmFactory.Write(realm => realm.Add(TestResources.CreateTestBeatmapSetInfo()));
+
+                var registration = realmFactory.Register(realm => realm.All<BeatmapSetInfo>(), onChanged);
+
+                testEventsArriving(true);
+
+                // All normal until here.
+                // Now let's yank the main realm context.
+                resolvedItems = null;
+                lastChanges = null;
+
+                using (realmFactory.BlockAllOperations())
+                    Assert.That(resolvedItems, Is.Empty);
+
+                realmFactory.Write(realm => realm.Add(TestResources.CreateTestBeatmapSetInfo()));
+
+                testEventsArriving(true);
+
+                // Now let's try unsubscribing.
+                resolvedItems = null;
+                lastChanges = null;
+
+                registration.Dispose();
+
+                realmFactory.Write(realm => realm.Add(TestResources.CreateTestBeatmapSetInfo()));
+
+                testEventsArriving(false);
+
+                // And make sure even after another context loss we don't get firings.
+                using (realmFactory.BlockAllOperations())
+                    Assert.That(resolvedItems, Is.Null);
+
+                realmFactory.Write(realm => realm.Add(TestResources.CreateTestBeatmapSetInfo()));
+
+                testEventsArriving(false);
+
+                void testEventsArriving(bool shouldArrive)
+                {
+                    realmFactory.Run(realm => realm.Refresh());
+
+                    if (shouldArrive)
+                        Assert.That(resolvedItems, Has.One.Items);
+                    else
+                        Assert.That(resolvedItems, Is.Null);
+
+                    realmFactory.Write(realm =>
+                    {
+                        realm.RemoveAll<BeatmapSetInfo>();
+                        realm.RemoveAll<RulesetInfo>();
+                    });
+
+                    realmFactory.Run(realm => realm.Refresh());
+
+                    if (shouldArrive)
+                        Assert.That(lastChanges?.DeletedIndices, Has.One.Items);
+                    else
+                        Assert.That(lastChanges, Is.Null);
+                }
+            });
+
+            void onChanged(IRealmCollection<BeatmapSetInfo> sender, ChangeSet? changes, Exception error)
+            {
+                if (changes == null)
+                    resolvedItems = sender;
+
+                lastChanges = changes;
+            }
+        }
+
+        [Test]
+        public void TestCustomRegisterWithContextLoss()
+        {
+            RunTestWithRealm((realmFactory, _) =>
+            {
+                BeatmapSetInfo? beatmapSetInfo = null;
+
+                realmFactory.Write(realm => realm.Add(TestResources.CreateTestBeatmapSetInfo()));
+
+                var subscription = realmFactory.Register(realm =>
+                {
+                    beatmapSetInfo = realm.All<BeatmapSetInfo>().First();
+
+                    return new InvokeOnDisposal(() => beatmapSetInfo = null);
+                });
+
+                Assert.That(beatmapSetInfo, Is.Not.Null);
+
+                using (realmFactory.BlockAllOperations())
+                {
+                    // custom disposal action fired when context lost.
+                    Assert.That(beatmapSetInfo, Is.Null);
+                }
+
+                // re-registration after context restore.
+                realmFactory.Run(realm => realm.Refresh());
+                Assert.That(beatmapSetInfo, Is.Not.Null);
+
+                subscription.Dispose();
+
+                Assert.That(beatmapSetInfo, Is.Null);
+
+                using (realmFactory.BlockAllOperations())
+                    Assert.That(beatmapSetInfo, Is.Null);
+
+                realmFactory.Run(realm => realm.Refresh());
+                Assert.That(beatmapSetInfo, Is.Null);
+            });
+        }
+    }
+}