TickSpec bullet points example with Active Pattern to convert string array to points

Bullets.feature

Feature: As a writer I like to use bullet points

Scenario: Writing lists with bullets
  Given a list of bullet points:
   * 1,2
   * 2,3
   * 3,4

BulletsSteps.fs

module BulletsSteps

type BulletsFixture () = inherit TickSpec.NUnit.FeatureFixture("Bullets.feature")

open TickSpec
open NUnit.Framework
  
let (|Int|_|) x =
    match System.Int32.TryParse(x) with
    | true, n -> Some n
    | false, _ -> None

let (|Points|) (bullets:string[]) =
    bullets |> Array.map (fun bullet ->
        let values = bullet.Split(',')
        match values with
        | [|Int x; Int y|] -> (x,y)
        | _ -> invalidOp "Expecting point"
    )

let [<Given>] ``a list of bullets points:`` (Points points) =
    for (x,y) in points do
        printf "%d %d" x y