https://gist.github.com/Gab-km/86dd730a8d8e407a699f に触発された何か

gistfile1.fs

type Case =
  | Value
  | Unit
 
type TestResult<'T> =
  | Success of 'T
  | Failure of string
 
type TestBuilder() =
  member this.Return(()) = Success ()
  member this.ReturnFrom(x, _) = x
  member this.Source(x: TestResult<unit>) = (x, Unit)
  member this.Source<'T>(x: TestResult<'T>) = (x, Value)
  member this.Bind(x, f: 'T -> TestResult<'U>) =
    match x with
    | Success x, _ -> f x
    | Failure x, Unit -> Failure x
    | Failure x, Value -> Failure x // AllResult [ f ? |> fst |> TestResult.cast; Failure x ]
  member this.Delay(f: unit -> TestResult<_>) = f
  member this.Run(f) =
    // なんとなくプリントしてるだけ
    // 他フレームワークに組み込みたいならコンストラクタでRunnerを受け取り、
    // 例外なげるなりなんなり
    f () |> printfn "%A"
 
let test = TestBuilder()
 
let example1 = test {
  return! Success 1
}
 
let example2 = test {
  do! Success ()
}
 
let example3 = test {
  do! Failure "test3"
  return! Success 2
}
 
// 失敗した後に使う引数がTestResultにないからまだ無理
let example4 = test {
  let! _ = Failure "test4"
  return! Success 2
}
 
let example5 = test {
  do! Success ()
  return! Success 2
}

https://gist.github.com/bleis-tift/a7a78d8122b99c083f1a を参考にがんばってみました