Added functioning tests.

osu.Game.Tests/Visual/Online/TestSceneChatManipulation.cs

@@ -3,16 +3,18 @@
 
 #nullable disable
 
+using System.Linq;
 using NUnit.Framework;
 using osu.Framework.Graphics;
 using osu.Game.Graphics;
 using osu.Game.Graphics.Sprites;
 using osu.Game.Overlays.Chat;
+using osuTK.Input;
 
 namespace osu.Game.Tests.Visual.Online
 {
     [TestFixture]
-    public class TestSceneChatManipulation : OsuTestScene
+    public class TestSceneChatManipulation : OsuManualInputManagerTestScene
     {
         private ChatTextBox box;
         private OsuSpriteText text;
@@ -41,6 +43,7 @@ namespace osu.Game.Tests.Visual.Online
                         Font = OsuFont.Default.With(size: 20),
                     }
                 };
+
                 box.OnCommit += (_, __) =>
                 {
                     text.Text = $"{nameof(box.OnCommit)}: {box.Text}";
@@ -48,27 +51,71 @@ namespace osu.Game.Tests.Visual.Online
                     box.TakeFocus();
                     text.FadeOutFromOne(1000, Easing.InQuint);
                 };
-            });
-        }
 
-        [Test]
+                box.TakeFocus();
-        public void TestReachingLimitOfMessages()
+            });
-        {
         }
 
         [Test]
         public void TestStayOnLastIndex()
         {
+            addMessages(2);
+            AddRepeatStep("Move to last", () => InputManager.Key(Key.Up), 2);
+
+            string lastText = string.Empty;
+            AddStep("Move up", () =>
+            {
+                lastText = box.Text;
+                InputManager.Key(Key.Up);
+            });
+
+            AddAssert("Text hasn't changed", () => lastText == box.Text);
         }
 
         [Test]
         public void TestKeepOriginalMessage()
         {
+            addMessages(1);
+            AddStep("Start writing", () => box.Text = "A random 文, ...");
+
+            AddStep("Move up", () => InputManager.Key(Key.Up));
+            AddStep("Rewrite old message", () => box.Text = "Old Message");
+
+            AddStep("Move back down", () => InputManager.Key(Key.Down));
+            AddAssert("Text back to previous", () => box.Text == "A random 文, ...");
         }
 
         [Test]
         public void TestResetIndexOnEmpty()
         {
+            addMessages(2);
+            AddRepeatStep("Move up", () => InputManager.Key(Key.Up), 2);
+            AddStep("Remove text", () => box.Text = string.Empty);
+
+            AddStep("Move up again", () => InputManager.Key(Key.Up));
+            AddAssert("Back to first message", () => box.Text == "Message 2");
+        }
+
+        [Test]
+        public void TestReachingLimitOfMessages()
+        {
+            addMessages(100);
+            AddAssert("List is full of <100-1>", () =>
+                Enumerable.Range(0, 100).Select(number => $"Message {100 - number}").SequenceEqual(box.MessageHistory));
+
+            addMessages(2);
+            AddAssert("List is full of <102-3>", () =>
+                Enumerable.Range(0, 100).Select(number => $"Message {102 - number}").SequenceEqual(box.MessageHistory));
+        }
+
+        private void addMessages(int count)
+        {
+            int iterations = 0;
+            AddRepeatStep("Add messages", () =>
+            {
+                box.Text = $"Message {++iterations}";
+                InputManager.Key(Key.Enter);
+            }, count);
         }
     }
 }

osu.Game/Graphics/UserInterface/HistoryTextBox.cs

@@ -7,56 +7,52 @@ using osuTK.Input;
 
 namespace osu.Game.Graphics.UserInterface
 {
-    public class MessageHistoryTextBox : FocusedTextBox
+    public class HistoryTextBox : FocusedTextBox
     {
         private readonly List<string> messageHistory = new List<string>();
 
-        private int messageIndex = -1;
+        public IReadOnlyList<string> MessageHistory => messageHistory;
+
+        private int historyIndex = -1;
 
         private string originalMessage = string.Empty;
 
-        public MessageHistoryTextBox()
+        public HistoryTextBox()
         {
             Current.ValueChanged += text =>
             {
                 if (string.IsNullOrEmpty(text.NewValue))
-                    messageIndex = -1;
+                    historyIndex = -1;
             };
         }
 
         protected override bool OnKeyDown(KeyDownEvent e)
         {
-            /* Behavior:
-             * add when on last element -> last element stays
-             * subtract when on first element -> sets to original text
-             * reset indexing when Text is set to Empty
-             */
-
             switch (e.Key)
             {
                 case Key.Up:
-                    if (messageIndex == -1)
+                    if (historyIndex == -1)
                         originalMessage = Text;
 
-                    if (messageIndex == messageHistory.Count - 1)
+                    if (historyIndex == messageHistory.Count - 1)
                         return true;
 
-                    Text = messageHistory[++messageIndex];
+                    Text = messageHistory[++historyIndex];
 
                     return true;
 
                 case Key.Down:
-                    if (messageIndex == -1)
+                    if (historyIndex == -1)
                         return true;
 
-                    if (messageIndex == 0)
+                    if (historyIndex == 0)
                     {
-                        messageIndex = -1;
+                        historyIndex = -1;
                         Text = originalMessage;
                         return true;
                     }
 
-                    Text = messageHistory[--messageIndex];
+                    Text = messageHistory[--historyIndex];
 
                     return true;
             }
@@ -69,7 +65,7 @@ namespace osu.Game.Graphics.UserInterface
             if (!string.IsNullOrEmpty(Text))
                 messageHistory.Insert(0, Text);
 
-            messageIndex = -1;
+            historyIndex = -1;
 
             base.Commit();
         }

osu.Game/Online/Chat/StandAloneChatDisplay.cs

@@ -120,7 +120,7 @@ namespace osu.Game.Online.Chat
             AddInternal(drawableChannel);
         }
 
-        public class ChatTextBox : MessageHistoryTextBox
+        public class ChatTextBox : HistoryTextBox
         {
             protected override bool OnKeyDown(KeyDownEvent e)
             {

osu.Game/Overlays/Chat/ChatTextBox.cs

@@ -7,7 +7,7 @@ using osu.Game.Resources.Localisation.Web;
 
 namespace osu.Game.Overlays.Chat
 {
-    public class ChatTextBox : MessageHistoryTextBox
+    public class ChatTextBox : HistoryTextBox
     {
         public readonly BindableBool ShowSearch = new BindableBool();