changes to make tests work

src/AddIns/DisplayBindings/WpfDesign/WpfDesign.Designer/Project/OutlineView/OutlineNode.cs

@@ -30,6 +30,7 @@ namespace ICSharpCode.WpfDesign.Designer.OutlineView
 		string Name { get; }
 		bool CanInsert(IEnumerable<IOutlineNode> nodes, IOutlineNode after, bool copy);
 		void Insert(IEnumerable<IOutlineNode> nodes, IOutlineNode after, bool copy);
+		ObservableCollection<IOutlineNode> Children{ get; }
 	}
 	
 

src/AddIns/DisplayBindings/WpfDesign/WpfDesign.Designer/Tests/Designer/OutlineView/HierarchyTests.cs

@@ -11,7 +11,7 @@ namespace ICSharpCode.WpfDesign.Tests.Designer.OutlineView
 	public class HierarchyTests : ModelTestHelper
 	{
 		private DesignItem _grid;
-		private OutlineNode _outline;
+		private IOutlineNode _outline;
 
 		[TestFixtureSetUp]
 		public void Intialize()

src/AddIns/DisplayBindings/WpfDesign/WpfDesign.Designer/Tests/Designer/OutlineView/InsertTests.cs

@@ -11,15 +11,15 @@ namespace ICSharpCode.WpfDesign.Tests.Designer.OutlineView
 	public class CollectionElementsInsertTests : ModelTestHelper
 	{
 		private DesignItem _grid;
-		private OutlineNode _outline;
+		private IOutlineNode _outline;
 
 		private DesignItem _gridButton;
 		private DesignItem _stackPanel;
 		private DesignItem _stackPanelButton;
 
-		private OutlineNode _gridButtonNode;
+		private IOutlineNode _gridButtonNode;
-		private OutlineNode _stackPanelNode;
+		private IOutlineNode _stackPanelNode;
-		private OutlineNode _stackPanelButtonNode;
+		private IOutlineNode _stackPanelButtonNode;
 
 		[SetUp]
 		public void Intialize()
@@ -147,15 +147,15 @@ namespace ICSharpCode.WpfDesign.Tests.Designer.OutlineView
 	public class ContentControlInsertTests : ModelTestHelper
 	{
 		private DesignItem _grid;
-		private OutlineNode _outline;
+		private IOutlineNode _outline;
 
 		private DesignItem _gridButton;
 		private DesignItem _stackPanel;
 		private DesignItem _stackPanelImage;
 
-		private OutlineNode _gridButtonNode;
+		private IOutlineNode _gridButtonNode;
-		private OutlineNode _stackPanelNode;
+		private IOutlineNode _stackPanelNode;
-		private OutlineNode _stackPanelImageNode;
+		private IOutlineNode _stackPanelImageNode;
 
 		[SetUp]
 		public void Intialize()

src/AddIns/DisplayBindings/WpfDesign/WpfDesign.Designer/Tests/Designer/OutlineView/SelectionTests.cs

@@ -11,7 +11,7 @@ namespace ICSharpCode.WpfDesign.Tests.Designer.OutlineView
 	public class SelectionTests : ModelTestHelper
 	{
 		private DesignItem _grid;
-		private OutlineNode _outline;
+		private IOutlineNode _outline;
 
 		[SetUp]
 		public void Intialize()