Implement copying of elements.

Tests/ViewModels/SettingsViewModelTest.cs

@@ -156,7 +156,33 @@ namespace Tests.ViewModels
         [Test]
         public void CopyElement()
         {
-            throw new NotImplementedException();
+            string testString = "this text should be duplicated";
+            _settingsVM.AddElementViewModel(
+                new ControlElementViewModel(new SelectEachDay(new Items(testString))));
+            int oldCount = _settingsVM.Elements.Count;
+            _settingsVM.Elements.First().IsSelected = true;
+            Assert.IsTrue(_settingsVM.CopyElementCommand.CanExecute(null),
+                "CopyElementCommand should be enabled.");
+            _settingsVM.CopyElementCommand.Execute(null);
+            Assert.AreEqual(oldCount + 1, _settingsVM.Elements.Count);
+
+            // Access the first element
+            ControlElementViewModel controlVM = _settingsVM.Elements.First() as ControlElementViewModel;
+            FormatElementViewModel formatVM = controlVM.Elements.First() as FormatElementViewModel;
+            Items items = formatVM.RevealModelObject() as Items;
+            Assert.IsNotNull(items,
+                "Child ViewModel of first ControlElementViewModel does not wrap Items object.");
+            Assert.AreEqual(testString, items.Content,
+                "First control element's child element has incorrect Content string.");
+
+            // Access the second element
+            controlVM = _settingsVM.Elements.Last() as ControlElementViewModel;
+            formatVM = controlVM.Elements.First() as FormatElementViewModel;
+            items = formatVM.RevealModelObject() as Items;
+            Assert.IsNotNull(items,
+                "Child ViewModel of last ControlElementViewModel does not wrap Items object.");
+            Assert.AreEqual(testString, items.Content,
+                "First control element's child element has incorrect Content string.");
         }
     }
 }