Add failing test

tests/Avalonia.Skia.UnitTests/Media/TextFormatting/TextShaperTests.cs

@@ -0,0 +1,43 @@
+using System;
+using System.Globalization;
+using Avalonia.Media;
+using Avalonia.Media.TextFormatting;
+using Avalonia.UnitTests;
+using Xunit;
+
+namespace Avalonia.Skia.UnitTests.Media.TextFormatting
+{
+    public class TextShaperTests
+    {
+        [Fact]
+        public void Should_Form_Clusters_For_BreakPairs()
+        {
+            using (Start())
+            {
+                var text = "\n\r\n".AsMemory();
+
+                var glyphRun = TextShaper.Current.ShapeText(
+                    text,
+                    Typeface.Default,
+                    12,
+                    CultureInfo.CurrentCulture);
+                
+                Assert.Equal(glyphRun.Characters.Length, text.Length);
+                Assert.Equal(glyphRun.GlyphClusters.Length, text.Length);
+                Assert.Equal(0, glyphRun.GlyphClusters[0]);
+                Assert.Equal(1, glyphRun.GlyphClusters[1]);
+                Assert.Equal(1, glyphRun.GlyphClusters[2]);
+            }
+        }
+        
+        private static IDisposable Start()
+        {
+            var disposable = UnitTestApplication.Start(TestServices.MockPlatformRenderInterface
+                .With(renderInterface: new PlatformRenderInterface(null),
+                    textShaperImpl: new TextShaperImpl(),
+                    fontManagerImpl: new CustomFontManagerImpl()));
+
+            return disposable;
+        }
+    }
+}