anchor.diff:  open Prime
   open Prime.Stream
   open Nu
  +open Nu.Simulants
   module WorldTests =
   
       let TestFilePath = "TestFile.nugame"
       let StringEvent = stoa<string> "String/Event"
  -    let Jim = Simulants.DefaultGroup => "Jim"
  -    let Bob = Simulants.DefaultGroup => "Bob"
  +    let Jim = DefaultGroup => "Jim"
  +    let Bob = DefaultGroup => "Bob"
   
       let [<Fact>] runOneFrameThenCleanUp () =
           let world = World.makeEmpty ()
  
positive.code:     let [<Fact>] entitySubscribeWorks () =
          let world = World.makeDefault ()
          let handleEvent = fun evt world -> (Cascade, World.updateUserState (fun _ -> evt.Subscriber) world)
          let world = World.subscribe handleEvent StringEvent Simulants.DefaultEntity world
          let world = World.publish String.Empty StringEvent EventTrace.empty Simulants.Game world
          Assert.Equal<Simulant> (Simulants.DefaultEntity :> Simulant, World.getUserState world)
  
      let [<Fact>] gameSerializationWorks () =
          let world = World.makeDefault ()
          let oldWorld = world
          World.writeGameToFile TestFilePath world
          let world = World.readGameFromFile TestFilePath world
          Assert.Equal<Name> (Simulants.DefaultScreen.GetName oldWorld, Simulants.DefaultScreen.GetName world)
          Assert.Equal<Name> (Simulants.DefaultGroup.GetName oldWorld, Simulants.DefaultGroup.GetName world)
          Assert.Equal<Name> (Simulants.DefaultEntity.GetName oldWorld, Simulants.DefaultEntity.GetName world)
  
      let [<Fact>] iterativeFrpWorks () =
          let world = World.makeDefault ()
          let world = World.createEntity typeof<EntityDispatcher>.Name None (Some Jim.EntityName) Simulants.DefaultGroup world |> snd
          let world = World.createEntity typeof<EntityDispatcher>.Name None (Some Bob.EntityName) Simulants.DefaultGroup world |> snd
          let world = !-- Bob.Visible --- map not --> Jim.Visible ^ world
          let world = Bob.SetVisible false world
          Assert.False (Bob.GetVisible world)
  
negative.code: 
      let [<Fact>] iterativeFrpCyclicWorks () =
          let world = World.makeDefault ()
          let world = World.createEntity typeof<EntityDispatcher>.Name None (Some Jim.EntityName) DefaultGroup world |> snd
          let world = World.createEntity typeof<EntityDispatcher>.Name None (Some Bob.EntityName) DefaultGroup world |> snd
          let world = !-- Bob.Visible --> Jim.Visible ^ world
          let world = !-- Jim.Visible -/> Bob.Visible ^ world
          let world = Bob.SetVisible false world
  