Add failing test cases

osu.Game.Tests/Visual/RealtimeMultiplayer/TestSceneRealtimeMultiplayer.cs

@@ -1,7 +1,9 @@
 // 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 NUnit.Framework;
 using osu.Game.Screens.Multi.Components;
+using osu.Game.Users;
 
 namespace osu.Game.Tests.Visual.RealtimeMultiplayer
 {
@@ -15,6 +17,28 @@ namespace osu.Game.Tests.Visual.RealtimeMultiplayer
             AddUntilStep("wait for loaded", () => multi.IsLoaded);
         }
 
+        [Test]
+        public void TestOneUserJoinedMultipleTimes()
+        {
+            var user = new User { Id = 33 };
+
+            AddRepeatStep("add user multiple times", () => Client.AddUser(user), 3);
+
+            AddAssert("room has 2 users", () => Client.Room?.Users.Count == 2);
+        }
+
+        [Test]
+        public void TestOneUserLeftMultipleTimes()
+        {
+            var user = new User { Id = 44 };
+
+            AddStep("add user", () => Client.AddUser(user));
+            AddAssert("room has 2 users", () => Client.Room?.Users.Count == 2);
+
+            AddRepeatStep("remove user multiple times", () => Client.RemoveUser(user), 3);
+            AddAssert("room has 1 user", () => Client.Room?.Users.Count == 1);
+        }
+
         private class TestRealtimeMultiplayer : Screens.Multi.RealtimeMultiplayer.RealtimeMultiplayer
         {
             protected override RoomManager CreateRoomManager() => new TestRealtimeRoomManager();

osu.Game/Tests/Visual/RealtimeMultiplayer/TestRealtimeMultiplayerClient.cs

@@ -31,7 +31,7 @@ namespace osu.Game.Tests.Visual.RealtimeMultiplayer
         public void RemoveUser(User user)
         {
             Debug.Assert(Room != null);
-            ((IMultiplayerClient)this).UserLeft(Room.Users.Single(u => u.User == user));
+            ((IMultiplayerClient)this).UserLeft(new MultiplayerRoomUser(user.Id));
 
             Schedule(() =>
             {