Add selection mask test cases

osu.Game/Tests/Visual/HitObjectSelectionMaskTestCase.cs

@@ -0,0 +1,47 @@
+// Copyright (c) 2007-2018 ppy Pty Ltd <contact@ppy.sh>.
+// Licensed under the MIT Licence - https://raw.githubusercontent.com/ppy/osu/master/LICENCE
+
+using osu.Framework.Allocation;
+using osu.Framework.Graphics;
+using osu.Framework.Graphics.Containers;
+using osu.Framework.Input.Events;
+using osu.Framework.Timing;
+using osu.Game.Rulesets.Edit;
+
+namespace osu.Game.Tests.Visual
+{
+    public abstract class HitObjectSelectionMaskTestCase : OsuTestCase
+    {
+        private SelectionMask mask;
+
+        protected override Container<Drawable> Content => content ?? base.Content;
+        private readonly Container content;
+
+        protected HitObjectSelectionMaskTestCase()
+        {
+            base.Content.Add(content = new Container
+            {
+                Clock = new FramedClock(new StopwatchClock()),
+                RelativeSizeAxes = Axes.Both
+            });
+        }
+
+        [BackgroundDependencyLoader]
+        private void load()
+        {
+            base.Content.Add(mask = CreateMask());
+            mask.SelectionRequested += (_, __) => mask.Select();
+
+            AddStep("Select", () => mask.Select());
+            AddStep("Deselect", () => mask.Deselect());
+        }
+
+        protected override bool OnClick(ClickEvent e)
+        {
+            mask.Deselect();
+            return true;
+        }
+
+        protected abstract SelectionMask CreateMask();
+    }
+}