Hedgehog

Features

• Integrated Shrinking — Generators produce rose trees of outcomes. Every generator shrinks for free — no manual shrink functions needed.
• Range-Controlled Generation — Numeric ranges separate bounds from origin, giving precise control over value distribution and shrink direction.
• Effects-Based Assertions — OCaml 5 algebraic effects keep generators and test logic cleanly separated. Use assert_, annotate, cover and more.
• State Machine Testing — Test stateful systems against abstract models with sequential and parallel linearizability checking.

Quick start

opam install hedgehog

open Hedgehog

let () =
  Property.check
    Property.(property Gen.(
      let* xs = list (Range.linear 0 100) (int (Range.linear 0 1000)) in
      return (fun () ->
        assert_ (List.rev (List.rev xs) = xs))))
  |> ignore