Add failing test

tests/Avalonia.Controls.UnitTests/TextBlockTests.cs

@@ -3,6 +3,7 @@ using Avalonia.Controls.Documents;
 using Avalonia.Controls.Templates;
 using Avalonia.Data;
 using Avalonia.Media;
+using Avalonia.Metadata;
 using Avalonia.Rendering;
 using Avalonia.UnitTests;
 using Moq;
@@ -165,9 +166,9 @@ namespace Avalonia.Controls.UnitTests
                         }.RegisterInNameScope(scope)
                 );
 
-                target.Inlines!.Add("123456");
+                target.Inlines!.AddText("123456");
                 target.Inlines.Add(new InlineUIContainer(button));
-                target.Inlines.Add("123456");
+                target.Inlines.AddText("123456");
 
                 target.Measure(Size.Infinity);
 
@@ -181,5 +182,26 @@ namespace Avalonia.Controls.UnitTests
                 Assert.Equal(60, button.Bounds.Left);
             }
         }
+
+        [Fact]
+        public void Setting_Text_Should_Reset_Inlines()
+        {
+            using (UnitTestApplication.Start(TestServices.StyledWindow))
+            {
+                var target = new TextBlock();
+
+                target.Inlines.Add(new Run("Hello World"));
+
+                Assert.Equal("Hello World", target.Text);
+
+                Assert.Equal(1, target.Inlines.Count);
+
+                target.Text = "1234";
+
+                Assert.Equal("1234", target.Text);
+
+                Assert.Equal(0, target.Inlines.Count);
+            }
+        }
     }
 }