anchor.diff:                      cts.Cancel()
                       do! a
                   }, cts.Token)
  -            forceAsync()
  +            do! Async.Sleep 500
               equal !cancelled true
               equal !ops "A"
           }
  
positive.code: open WebSharper
  open WebSharper.JavaScript
  open WebSharper.Testing
  
  [<Inline "WebSharper.Concurrency.scheduler().tick()">]
  let tick() = ()
  
  [<Inline "WebSharper.Concurrency.scheduler().idle">]
  let isIdle() = true
  
  [<JavaScript>]
  let forceAsync() =
      while not (isIdle()) do tick()
  
  type Message =
      | Increment of int
  
negative.code:             let errorCatched = ref false
              mb.Error.Add (fun _ -> errorCatched := true)
              mb.Post(Die)
              do! Async.Sleep 500
              equal !errorCatched true
          }
  
  