Added failing test for AvaloniaList.CopyTo.

`Can_CopyTo_Array_Of_Same_Type` passes but `Can_CopyTo_Array_Of_Base_Type` fails.

.ncrunch/Avalonia.Controls.UnitTests.net47.v3.ncrunchproject

@@ -3,5 +3,6 @@
     <HiddenComponentWarnings>
       <Value>MissingOrIgnoredProjectReference</Value>
     </HiddenComponentWarnings>
+        <FixtureName>Avalonia.Controls.UnitTests.TimePickerTests</FixtureName>
   </Settings>
 </ProjectConfiguration>

tests/Avalonia.Base.UnitTests/Collections/AvaloniaListTests.cs

@@ -1,4 +1,5 @@
 using System;
+using System.Collections;
 using System.Collections.Generic;
 using System.Collections.Specialized;
 using System.ComponentModel;
@@ -334,5 +335,27 @@ namespace Avalonia.Base.UnitTests.Collections
 
             Assert.True(raised);
         }
+
+        [Fact]
+        public void Can_CopyTo_Array_Of_Same_Type()
+        {
+            var target = new AvaloniaList<string> { "foo", "bar", "baz" };
+            var result = new string[3];
+
+            target.CopyTo(result, 0);
+
+            Assert.Equal(target, result);
+        }
+
+        [Fact]
+        public void Can_CopyTo_Array_Of_Base_Type()
+        {
+            var target = new AvaloniaList<string> { "foo", "bar", "baz" };
+            var result = new object[3];
+
+            ((IList)target).CopyTo(result, 0);
+
+            Assert.Equal(target, result);
+        }
     }
 }