Add a failing test

tests/Avalonia.Markup.Xaml.UnitTests/Xaml/IgnoredDirectivesTests.cs

@@ -0,0 +1,31 @@
+using Avalonia.Controls;
+using Avalonia.Controls.Presenters;
+using Avalonia.UnitTests;
+using Xunit;
+
+namespace Avalonia.Markup.Xaml.UnitTests.Xaml
+{
+    public class IgnoredDirectivesTests : XamlTestBase
+    {
+        [Fact]
+        public void Ignored_Directives_Should_Compile()
+        {
+            using (UnitTestApplication.Start(TestServices.StyledWindow))
+            {
+                const string xaml = @"
+<Window xmlns='https://github.com/avaloniaui'
+        xmlns:sys='clr-namespace:System;assembly=netstandard'
+        xmlns:x='http://schemas.microsoft.com/winfx/2006/xaml'>
+    <TextBlock x:Name='target' x:FieldModifier='Public' Text='Foo'/>
+</Window>";
+                var window = (Window)AvaloniaRuntimeXamlLoader.Load(xaml);
+                var target = window.FindControl<TextBlock>("target");
+
+                window.ApplyTemplate();
+                target.ApplyTemplate();
+
+                Assert.Equal("Foo", target.Text);
+            }
+        }
+    }
+}