anchor.diff:      let tree = new WatchTreeView()
       tree.Watch("w1", 1)
       tree.Watch("w1", 2)
  +    
       test <@ tree.Nodes.Count = 1 @>
       test <@ tree.Nodes.Find("w1", false).Length = 1 @>
       test <@ ((tree.Nodes.Find("w1", false).[0].Tag :?> Watch).RootInfo.Value :?> int) = 2 @>
  
positive.code: let ``calling Watch with new name adds a node`` () =
      let tree = new WatchTreeView()
      tree.Watch("w1", 1)
      test <@ tree.Nodes.Count = 1 @>
      test <@ tree.Nodes.Find("w1", false) <> null @>
  
  
negative.code:     let tree = new WatchTreeView()
      tree.Watch("w1", 1)
      tree.Watch("w2", 2)
      
      test <@ tree.Nodes.Count = 2 @>
      test <@ tree.Nodes.Find("w1", false).Length = 1 @>
      test <@ tree.Nodes.Find("w2", false).Length = 1 @>
  