Added failing test for #1765.

tests/Avalonia.Controls.UnitTests/ApplicationTests.cs

@@ -113,5 +113,21 @@ namespace Avalonia.Controls.UnitTests
                 Assert.Throws<ArgumentNullException>(() => { Application.Current.Run(null); });
             }
         }
+
+        [Fact]
+        public void Raises_ResourcesChanged_When_Event_Handler_Added_After_Resources_Has_Been_Accessed()
+        {
+            // Test for #1765.
+            using (UnitTestApplication.Start())
+            {
+                var resources = Application.Current.Resources;
+                var raised = false;
+
+                Application.Current.ResourcesChanged += (s, e) => raised = true;
+                resources["foo"] = "bar";
+
+                Assert.True(raised);
+            }
+        }
     }
-}
+}