FsCheck example

fscheck_example.fs

module FsCheckExample

open System.IO
open NUnit.Framework
open FsCheck.NUnit
open FsCheck.PropOperators
open FsCheck.GenBuilder
open FsCheck

[<Property(Verbose = true, Replay = "(1593021609, 297184309)")>]
let ``FsCheck example`` (xs: int list) =
    xs |> List.rev = xs

[<Property(Verbose = true)>]
let ``FsCheck example 2`` (xs: float list) =
    xs |> List.rev |> List.rev = xs


[<Property(Verbose = true)>]
let ``FsCheck example 3`` (xs: float list) =
    (xs |> List.forall (System.Double.IsRealNumber)) ==>
        lazy (xs |> List.rev |> List.rev = xs)

let realFloatGen =
    gen {
            let! xs = Arb.generate<float> |> Gen.filter System.Double.IsRealNumber |> Gen.nonEmptyListOf
            return xs
        }

[<Test>]
let ``FsCheck example 4``() =
    let property xs = xs |> List.rev |> List.rev = xs
    property |> Prop.forAll (Arb.fromGen realFloatGen) |> Check.VerboseThrowOnFailure

type MyGenerators =
  static member RealFloat() =
      {new Arbitrary<float list>() with
          override x.Generator = realFloatGen
          override x.Shrinker t = base.Shrinker t }

[<Property(Verbose = true, Arbitrary = [|typeof<MyGenerators>|])>]
let ``FsCheck example 5`` (xs: float list) =
    xs |> List.rev |> List.rev = xs