Add test for changing item in list

Brought forward from https://github.com/ppy/osu/pull/32250.

osu.Game.Tests/Visual/Multiplayer/TestSceneMultiplayerQueueList.cs

@@ -49,13 +49,15 @@ namespace osu.Game.Tests.Visual.Multiplayer
 
             AddStep("create playlist", () =>
             {
-                Child = playlist = new MultiplayerQueueList(room)
+                Child = playlist = new MultiplayerQueueList
                 {
                     Anchor = Anchor.Centre,
                     Origin = Anchor.Centre,
-                    Size = new Vector2(500, 300),
+                    Size = new Vector2(500, 300)
                 };
 
+                playlist.Items.ReplaceRange(0, playlist.Items.Count, MultiplayerClient.ClientAPIRoom!.Playlist);
+
                 MultiplayerClient.ClientAPIRoom!.PropertyChanged += (_, e) =>
                 {
                     if (e.PropertyName == nameof(Room.Playlist))
@@ -132,6 +134,18 @@ namespace osu.Game.Tests.Visual.Multiplayer
             assertDeleteButtonVisibility(1, false);
         }
 
+        [Test]
+        public void TestChangeExistingItem()
+        {
+            AddStep("change beatmap", () => MultiplayerClient.EditPlaylistItem(new MultiplayerPlaylistItem
+            {
+                ID = playlist.Items[0].ID,
+                BeatmapID = 1337
+            }).WaitSafely());
+
+            AddUntilStep("first playlist item has new beatmap", () => playlist.Items[0].Beatmap.OnlineID, () => Is.EqualTo(1337));
+        }
+
         private void addPlaylistItem(Func<int> userId)
         {
             long itemId = -1;