anchor.diff:      world
   
     let addWallNorth = (World.addWall WallPositions.North pos)
  -  let asserWallNorth = map (assertAddingWalls WallPositions.North)
  +  let assertWallNorth = map (assertAddingWalls WallPositions.North)
     let addWallSouth = bind (World.addWall WallPositions.South pos)
     let assertWallsNorthAndSouth = map (assertAddingWalls (WallPositions.North ||| WallPositions.South))
   
  -  let testFn = 
  -    addWallNorth
  -    >> asserWallNorth
  -    >> addWallSouth
  -    >> assertWallsNorthAndSouth
  -    >> ignore
  -
  -  testFn world
  +  world
  +    |> addWallNorth
  +    |> assertWallNorth
  +    |> addWallSouth
  +    |> assertWallsNorthAndSouth
  +    |> assertResult
  +    |> ignore
     
   [<Test>]
   let ``Adding a wall outside of the world should testFail``() =
     let world = World.Default
  -  
     let pos = (200u, 200u)
  -  let result = World.addWall WallPositions.North pos world
  -  match result with 
  -  | Failure _ -> testSuccess()
  -  | Success _ -> testFail()
  +  
  +  World.addWall WallPositions.North pos world |> either testFail testSuccess
   
   [<Test>]
   let ``hasWall should work``() =
  
positive.code: open FsUnit
  open FsKarel.Core
  
  let testFail() = true |> should be False
  let testSuccess() = true |> should be True
  
  [<Test>]
  let ``Addition of walls to a world should work``() =
  
negative.code: [<Test>]
  let ``Addition of beepers to a world should work``() =
    let world = World.Default
    let pos = (3u, 3u)
    
    let assertBeepers expected world =
      Map.containsKey pos world.beepers |> should be True
      let beepers = Map.find pos world.beepers
      beepers |> should equal expected
      world
    
    world.beepers |> should equal Map.empty
  
    world
      |> World.setBeepers 5u pos
      |> map (assertBeepers 5u)
      |> bind (World.setBeepers 8u pos)
      |> map (assertBeepers 8u)
      |> assertResult
      |> ignore
    
  [<Test>]
  let ``Adding a beeper outside of the world should testFail``() =
    let world = World.Default
    let pos = (200u, 200u)
    
    World.setBeepers 5u pos world |> assertResult |> ignore
  
  [<Test>]
  let ``hasBeeper should work``() =
    let world = World.Default
    let pos = (3u, 3u)
    
    match World.hasBeepers pos world with 
      | Failure _ -> testFail()
      | Success r -> r |> should be False
  