anchor.diff:  open System.Reflection
   open System.Diagnostics
   open System.Threading
  +open System.Threading.Tasks
   
   // TODO: move to internal
   type SourceLocation =
  
positive.code:                       s=InParallel ||
                        not(Seq.exists (fun t -> t.sequenced=s) runningTests)
                      )
                   |> asyncRun (fun cancel ->
                        Async.foldParallelLimitWithCancel cancel
                                  (numberOfWorkers true config)
                      ) (runningTests,results,maxMemory)
               )
  
        w.Stop()
  
negative.code:             TestSummary.single (TestResult.Error e) (float w.ElapsedMilliseconds)
      }
  
    let private numWorkers limit config =
      if config.parallelWorkers < 0 then
        -config.parallelWorkers * Environment.ProcessorCount
      elif config.parallelWorkers = 0 then
  