anchor.diff:  
       new () = PropertyDiscoverer(null)
   
  -    member x.MessageSink = messageSink
  +    member __.MessageSink = messageSink
   
       interface IXunitTestCaseDiscoverer with
  -        override this.Discover(discoveryOptions:ITestFrameworkDiscoveryOptions, testMethod:ITestMethod, factAttribute:IAttributeInfo)=
  +        override this.Discover(discoveryOptions:ITestFrameworkDiscoveryOptions, testMethod:ITestMethod, _:IAttributeInfo)=
               let ptc = new PropertyTestCase(this.MessageSink, discoveryOptions.MethodDisplayOrDefault(), testMethod)
               Seq.singleton (ptc :> IXunitTestCase)
positive.code:                           | TestResult.True _ ->
                              let output = Runner.onFinishedToString "" xunitRunner.Result
                              new TestPassed(test, timer.Total, output) :> TestResultMessage
                            | TestResult.Exhausted testdata ->
                              summary.Failed <- summary.Failed + 1
                              upcast new TestFailed(test, timer.Total, "", new PropertyFailedException(xunitRunner.Result))
                            | TestResult.False (testdata, originalArgs, shrunkArgs, Outcome.Exception e, seed)  ->
                              summary.Failed <- summary.Failed + 1
                              let message = sprintf "%s%s" Environment.NewLine (Runner.onFailureToString "" testdata originalArgs shrunkArgs seed)
                              upcast new TestFailed(test, timer.Total, "", new PropertyFailedException(message, e))
                            | TestResult.False (testdata, originalArgs, shrunkArgs, outcome, seed)  ->
                              summary.Failed <- summary.Failed + 1
                              upcast new TestFailed(test, timer.Total, "", new PropertyFailedException(xunitRunner.Result))
                  with
  
negative.code: //can not be an anonymous type because of let mutable.
  type XunitRunner() =
      let mutable result = None
      member __.Result = result.Value
      interface IRunner with
          override __.OnStartFixture _ = ()
          override __.OnArguments (ntest,args, every) =
              printf "%s" (every ntest args)
          override __.OnShrink(args, everyShrink) =
              printf "%s" (everyShrink args)
          override __.OnFinished(_ ,testResult) =
              result <- Some testResult
  
  ///Override Arbitrary instances for FsCheck tests within the attributed class
  