anchor.diff:  
   [<Test>]
   let part1() =
  -    ClubbedToDeath.costToEnter Dave |> shouldEqual (Choice2Of2 "Too old!")
  -    ClubbedToDeath.costToEnter Ken |> shouldEqual (Choice1Of2 5m)
  -    ClubbedToDeath.costToEnter Ruby |> shouldEqual (Choice1Of2 0m)
  -    ClubbedToDeath.costToEnter { Ruby with Age = 17 } |> shouldEqual (Choice2Of2 "Too young!")
  -    ClubbedToDeath.costToEnter { Ken with Sobriety = Unconscious } |> shouldEqual (Choice2Of2 "Sober up!")
  +    ClubbedToDeath.costToEnter Dave |> shouldEqual (Failure "Too old!")
  +    ClubbedToDeath.costToEnter Ken |> shouldEqual (Success 5m)
  +    ClubbedToDeath.costToEnter Ruby |> shouldEqual (Success 0m)
  +    ClubbedToDeath.costToEnter { Ruby with Age = 17 } |> shouldEqual (Failure "Too young!")
  +    ClubbedToDeath.costToEnter { Ken with Sobriety = Unconscious } |> shouldEqual (Failure "Sober up!")
   
   (**
    * The thing to note here is how the Validations can be composed together in a computation expression.
  
positive.code: // And the use? Dave tried the second nightclub after a few more drinks in the pub
  [<Test>]
  let part2() =
      ClubTropicana.costToEnter { Dave with Sobriety = Paralytic } |> shouldEqual (Choice2Of2 ["Too old!"; "Sober up!"])
      ClubTropicana.costToEnter Ruby |> shouldEqual (Choice1Of2 0m)
  
  (**
   *
  
negative.code:     open Club
      let checkGender (p: Person) =
          match p.Gender with
          | Male -> Success p
          | _ -> Failure "Men only"
  
      let costToEnter p =
          [checkAge; checkClothes; checkSobriety; checkGender]
  