Add simple test case for FullscreenOverlay

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

@@ -0,0 +1,40 @@
+// 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.Framework.Graphics;
+using osu.Framework.Graphics.Shapes;
+using osu.Game.Overlays;
+using osuTK.Graphics;
+
+namespace osu.Game.Tests.Visual.Online
+{
+    [TestFixture]
+    public class TestCaseFullscreenOverlay : OsuTestCase
+    {
+        private FullscreenOverlay overlay;
+
+        protected override void LoadComplete()
+        {
+            base.LoadComplete();
+
+            Add(overlay = new TestFullscreenOverlay());
+            AddStep(@"toggle", overlay.ToggleVisibility);
+        }
+
+        private class TestFullscreenOverlay : FullscreenOverlay
+        {
+            public TestFullscreenOverlay()
+            {
+                Children = new Drawable[]
+                {
+                    new Box
+                    {
+                        Colour = Color4.Black,
+                        RelativeSizeAxes = Axes.Both,
+                    },
+                };
+            }
+        }
+    }
+}