npx claudepluginhub nwave-ai/nwave --plugin nwThis skill uses the workspace's default tool permissions.
| Framework | Language | Shrinking | Stateful | Parallel | Choose When |
Guides Haskell property-based testing with QuickCheck and Hedgehog, covering generators, shrinking, framework selection, and stateful testing.
Generates property-based tests using fast-check (TypeScript/JavaScript with Vitest) and Hypothesis (Python) to find edge cases, verify properties like roundtrips and invariants.
Writes property-based tests using Hegel for Rust, Go, and C++ projects. Useful for testing invariants, round-trips, contracts via generative inputs, fuzzing, and shrinking.
Share bugs, ideas, or general feedback.
| Framework | Language | Shrinking | Stateful | Parallel | Choose When |
|---|---|---|---|---|---|
| FsCheck | C#/F# | Type-based | No | No | F#-first projects, or C# needing mature PBT |
| CsCheck | C# | PCG-based | Yes | Yes (linearizability) | C# projects needing concurrent testing |
| fsharp-hedgehog | F# | Integrated | No | No | F# projects wanting modern integrated shrinking |
C# default: CsCheck (better shrinking, stateful + parallel). F# default: FsCheck or fsharp-hedgehog.
// C#
using FsCheck; using FsCheck.Xunit;
public class SortProperties
{
[Property]
public bool SortPreservesLength(List<int> xs) =>
xs.OrderBy(x => x).Count() == xs.Count;
}
// F#
open FsCheck
let propSortIdempotent (xs: int list) =
List.sort (List.sort xs) = List.sort xs
Check.Quick propSortIdempotent
Arb.Generate<int>() // any int
Gen.Choose(0, 100) // bounded
Arb.Generate<string>()
Arb.Generate<List<int>>()
// Custom generator
public static Arbitrary<Email> EmailArb() =>
Arb.From(
from name in Arb.Generate<NonEmptyString>()
select new Email($"{name}@example.com")
);
Arb.Register<MyGenerators>(); // register custom arbitraries
Gen.choose (0, 100)
Gen.elements [1; 2; 3]
Gen.oneof [gen1; gen2]
Gen.frequency [(80, gen1); (20, gen2)]
Gen.listOf (Gen.choose (0, 100))
Gen.choose (0, 100) |> Gen.map (fun x -> x * 2)
gen {
let! xs = Gen.listOf (Gen.choose (0, 100))
let! x = Gen.elements xs
return (xs, x)
}
using CsCheck;
[Fact]
public void Sort_Preserves_Length()
{
Gen.Int.Array
.Sample(arr => arr.OrderBy(x => x).Count() == arr.Length);
}
Gen.Int // any int
Gen.Int[0, 100] // bounded
Gen.Double
Gen.String
Gen.Bool
Gen.Int.Array // int[]
Gen.Int.List // List<int>
Gen.Int.HashSet // HashSet<int>
Gen.Int.Select(x => x * 2) // map
Gen.Select(Gen.String, Gen.Int, (name, age) => new User(name, age))
Gen.OneOf(Gen.Int.Select(x => (object)x), Gen.String.Select(x => (object)x))
Gen.Int.Where(x => x > 0) // filter
FsCheck: No stateful testing support. Use CsCheck for stateful and parallel testing. fsharp-hedgehog: No stateful testing support.
[Fact]
public void Store_Matches_Model()
{
Gen.Int.List[0, 100].Sample(operations =>
{
var store = new MyStore();
var model = new Dictionary<string, int>();
// CsCheck uses operation sequences with Check.Sample
});
}
[Fact]
public void Store_Is_Linearizable()
{
Check.SampleConcurrent(
Gen.Operation<MyStore>(/* ... */),
initialState: () => new MyStore()
);
}
Check.SampleConcurrent runs operations sequentially then in parallel, checking against all possible linearizations. Shrinking works for parallel failures -- rare among PBT frameworks.
open Hedgehog
let propReverse = property {
let! xs = Gen.list (Range.linear 0 100) Gen.alpha
return List.rev (List.rev xs) = xs
}
Property.check propReverse
Gen.int (Range.linear 0 100)
Gen.string (Range.linear 0 50) Gen.alpha
Gen.bool
Gen.list (Range.linear 0 50) (Gen.int (Range.linear 0 100))
Gen.option (Gen.int (Range.linear 0 100))
<!-- FsCheck -->
<PackageReference Include="FsCheck.Xunit" Version="3.0.0" />
<!-- CsCheck -->
<PackageReference Include="CsCheck" Version="4.0.0" />
<!-- fsharp-hedgehog -->
<PackageReference Include="Hedgehog" Version="0.13.0" />
<PackageReference Include="Hedgehog.Xunit" Version="0.5.0" />
<!-- All work with xUnit, NUnit, MSTest (CsCheck/FsCheck) -->
Prop.When for preconditions with automatic discard trackingProp.ForAll with Command for lightweight model checkingProp.Collect and Prop.ClassifyCheck.SampleConcurrent -- rare capabilityCheck.Faster for comparative benchmarksCheck.CausalProfilinggen { }, property { } -- most readable F# PBT syntax