anchor.diff:                      |> List.map (fun x -> x.Id)
                       |> List.max
               (fun items ->
  -              { Id = maxId + 1
  -                Name = model.Input
  -                Done = false
  -                IsEditing = false} :: items)
  +                items @ [{  Id = maxId + 1
  +                            Name = model.Input
  +                            Done = false
  +                            IsEditing = false}])
               |> updateItems {model with Input = ""}
           | ChangeInput v -> {model with Input = v}
           | MarkAsDone i ->
  
positive.code: 
      let model' =
          match msg with
          | AddItem ->
              let maxId =
                  if model.Items |> List.isEmpty then 1
  
negative.code: 
  // Todo update
  type TodoAction =
      | NoOp
      | AddItem
      | ChangeInput of string
      | MarkAsDone of Item
  