Integrates polytropos open records and variants with QuickCheck property-based testing.

Architectural Overview & Rationale

Records

'Arbitrary (Record r)' generates each field value via that field's own Arbitrary instance (the walk is heterogeneous: rows may freely mix field types) and packs the results straight into the contiguous SmallArray payload — with no intermediate tuples or generic-representation trees.

Shrinking is slot-indexed: each field slot is shrunk independently, one field at a time, so shrinking a \(k\)-field record yields \(O(k)\) candidates per level instead of the full Cartesian product over per-field shrink lists.

Variants

'Arbitrary (Variant s)' uniformly selects a constructor tag index and generates that constructor's payload fields. Shrinking is branch-preserving: only the payload of the currently active constructor is shrunk; the tag never changes, so a counterexample stays on the constructor branch that triggered the property failure.

When to Use This Module

• When property-testing systems that use polytropos open records and variants.

{-# LANGUAGE DataKinds #-}
{-# LANGUAGE OverloadedRecordDot #-}
{-# LANGUAGE TypeApplications #-}

import Test.QuickCheck
import Polytropos
import Polytropos.QuickCheck

type User = Record '["id" ':= Int, "active" ':= Bool]

prop_userPositiveId :: Property
prop_userPositiveId = forAll (arbitrary @User) $ \u ->
  u.id == u.id