Use custom FsCheck Arbitrary in testProperty

I have this code:

type 'a ClusteredList = ClusteredList of 'a list

let private clusteredListGen =
    gen {
        let! clusterValues = Arb.generate<int> |> Gen.listOf |> Gen.filter (fun x -> x.Length < 10)
        let! res =
            clusterValues
            |> List.map (Gen.constant >> Gen.nonEmptyListOf)
            |> List.fold (fun acc x -> gen {
                 let! acc = acc
                 let! x = x
                 return acc @ x }) 
               (Gen.constant [])
        return ClusteredList res
    } |> Arb.fromGen

testCase "concat = original seq" <| fun _ ->
    let prop (ClusteredList xs) =
        xs |> Seq.groupClusteredBy id id |> Seq.collect snd |> Seq.toList = xs
    Check.QuickThrowOnFailure (Prop.forAll clusteredListGen prop)

Is it possible to rewrite it with testProperty? I tried:

let private clusteredListConfig = { FsCheckConfig.defaultConfig with arbitrary =  FsCheckConfig.defaultConfig.arbitrary @ [??????] }
testPropertyWithConfig clusteredListConfig "test" <| fun _ -> ...

arbitrary is a list of Types, I have a value of Arbitrary<_> instance. Any ideas how to pass it to config?

[haf]

Meta: I’m not going to contribute to more fragmentation by supporting a library that seemingly doesn’t send pull requests towards FsCheck. If it wants to remodel FsCheck then that should be a pull request first, being rejected (like this project was with Fuchu).

On topic: so the only difference there is really Prop.ForAll versus property {} – because the generators can be used and consumed with a workflow builder in FsCheck as well? That the sample uses operators instead of a workflow builder doesn’t change that (but does make the two snippets read very differently)

[AnthonyLloyd]

Closing this as Arbitrary is not recommended and won’t be support in future FsCheck.

I’ve added an explanation to the docs and the following issues explain in detail in #201 and fscheck/FsCheck#413.