Add test scene for Triangles

osu.Game.Tests/Visual/Background/TestSceneTrianglesBackground.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 osu.Game.Graphics.Backgrounds;
+using osu.Framework.Graphics;
+using osuTK.Graphics;
+using osu.Framework.Graphics.Shapes;
+
+namespace osu.Game.Tests.Visual.Background
+{
+    public class TestSceneTrianglesBackground : OsuTestScene
+    {
+        private readonly Triangles triangles;
+
+        public TestSceneTrianglesBackground()
+        {
+            Children = new Drawable[]
+            {
+                new Box
+                {
+                    RelativeSizeAxes = Axes.Both,
+                    Colour = Color4.Black
+                },
+                triangles = new Triangles
+                {
+                    RelativeSizeAxes = Axes.Both,
+                    ColourLight = Color4.White,
+                    ColourDark = Color4.Gray
+                }
+            };
+        }
+
+        protected override void LoadComplete()
+        {
+            base.LoadComplete();
+
+            AddSliderStep("Triangle scale", 0f, 10f, 1f, s => triangles.TriangleScale = s);
+        }
+    }
+}