Added a few StringTokenizer tests.

tests/Avalonia.Base.UnitTests/Utilities/StringTokenizerTests.cs

@@ -0,0 +1,69 @@
+using System;
+using Avalonia.Utilities;
+using Xunit;
+
+namespace Avalonia.Base.UnitTests.Utilities
+{
+    public class StringTokenizerTests
+    {
+        [Fact]
+        public void ReadInt32_Reads_Values()
+        {
+            var target = new StringTokenizer("123,456");
+
+            Assert.Equal(123, target.ReadInt32());
+            Assert.Equal(456, target.ReadInt32());
+            Assert.Throws<FormatException>(() => target.ReadInt32());
+        }
+
+        [Fact]
+        public void ReadDouble_Reads_Values()
+        {
+            var target = new StringTokenizer("12.3,45.6");
+
+            Assert.Equal(12.3, target.ReadDouble());
+            Assert.Equal(45.6, target.ReadDouble());
+            Assert.Throws<FormatException>(() => target.ReadDouble());
+        }
+
+        [Fact]
+        public void TryReadInt32_Reads_Values()
+        {
+            var target = new StringTokenizer("123,456");
+
+            Assert.True(target.TryReadInt32(out var value));
+            Assert.Equal(123, value);
+            Assert.True(target.TryReadInt32(out value));
+            Assert.Equal(456, value);
+            Assert.False(target.TryReadInt32(out value));
+        }
+
+        [Fact]
+        public void TryReadInt32_Doesnt_Throw()
+        {
+            var target = new StringTokenizer("abc");
+
+            Assert.False(target.TryReadInt32(out var value));
+        }
+
+        [Fact]
+        public void TryReadDouble_Reads_Values()
+        {
+            var target = new StringTokenizer("12.3,45.6");
+
+            Assert.True(target.TryReadDouble(out var value));
+            Assert.Equal(12.3, value);
+            Assert.True(target.TryReadDouble(out value));
+            Assert.Equal(45.6, value);
+            Assert.False(target.TryReadDouble(out value));
+        }
+
+        [Fact]
+        public void TryReadDouble_Doesnt_Throw()
+        {
+            var target = new StringTokenizer("abc");
+
+            Assert.False(target.TryReadDouble(out var value));
+        }
+    }
+}