anchor.diff:            fun () ->
               match x.Run() with
               | Done (meta, (Passed value, []), duration) ->
  -                let watch = Stopwatch()
  -                watch.Start()
  +                let watch = Stopwatch.StartNew()
                   try (rest value).Run()
                   with e ->
                     watch.Stop()
  
positive.code:                 // even if the assertion is not passed,
                  // the test is continuable.
                  // So, continue the test.
                  let watch = Stopwatch()
                  try
                    assert (typeof<'T> = typeof<unit>)
                    watch.Start()
                    // continue th test!
                    let testRes = (rest Unchecked.defaultof<'T>).Run()
                    match results with
  
negative.code:           fun () ->
              match x.Run() with
              | Done (meta, (Passed unit, []), duration) ->
                  let watch = Stopwatch.StartNew()
                  try (rest unit).Run() |> TestResult.addDuration duration
                  with e ->
                    watch.Stop()
  