Add test coverage

osu.Game.Tests/Visual/Collections/TestSceneManageCollectionsDialog.cs

@@ -44,7 +44,7 @@ namespace osu.Game.Tests.Visual.Collections
             {
                 manager = new CollectionManager(LocalStorage),
                 Content,
-                dialogOverlay = new DialogOverlay()
+                dialogOverlay = new DialogOverlay(),
             });
 
             Dependencies.Cache(manager);
@@ -134,6 +134,27 @@ namespace osu.Game.Tests.Visual.Collections
             assertCollectionName(0, "2");
         }
 
+        [Test]
+        public void TestCollectionNameCollisions()
+        {
+            AddStep("add dropdown", () =>
+            {
+                Add(new CollectionFilterDropdown
+                    {
+                        Anchor = Anchor.TopRight,
+                        Origin = Anchor.TopRight,
+                        RelativeSizeAxes = Axes.X,
+                        Width = 0.4f,
+                    }
+                );
+            });
+            AddStep("add two collections with same name", () => manager.Collections.AddRange(new[]
+            {
+                new BeatmapCollection { Name = { Value = "1" } },
+                new BeatmapCollection { Name = { Value = "1" }, Beatmaps = { beatmapManager.GetAllUsableBeatmapSets().First().Beatmaps[0] } },
+            }));
+        }
+
         [Test]
         public void TestRemoveCollectionViaButton()
         {