anchor.diff:               collection.Add v |> ignore
           ) |> ignore
   
  -//        let mutable result = 0
  -//        let resultCb = derived |>  Mod.unsafeRegisterCallbackKeepDisposable (fun v ->
  -//            result <- v
  -//        )
  +        let mutable result = 0
  +        let resultCb = derived |>  Mod.unsafeRegisterCallbackKeepDisposable (fun v ->
  +            result <- v
  +        )
   
           let mutable r = 0
           let puller = System.Threading.Thread(ThreadStart(fun _ ->
  
positive.code:                 r <- derived |> Mod.force
          ))
  
          puller.Start()
          middle.Start()
          inputThread.Start()
  
negative.code: 
          //collection.Count |> should equal 0
          printfn "awaited"
          result |> should equal currentValue
          derived |> Mod.force |> should equal currentValue
          printfn "done"
  
  