Changelog

All notable changes to hedgehog-lockstep will be documented in this file.

The format follows Keep a Changelog, and this project adheres to Haskell PVP.

0.1.0.0

Initial release.

Added

• LockstepCmd record bundling an API operation with its model interpretation and observation.
• LockstepState wrapping a user-defined model plus a ModelEnv, a Map keyed by Hedgehog Var identity (O(log n) lookup) using a phase-polymorphic Ord1-based comparison. initialLockstepState, getModel, and getEntries construct and project from it.
• GVar and Op (OpId, OpFst, OpSnd, OpLeft, OpRight, OpComp, plus (>>>) for left-to-right composition) for projecting values out of compound action outputs.
• varsOfType, mkGVar, mkGVarId, mapGVar, resolveGVar, concreteGVar, gvarLabel for enumerating and resolving generalized variables. mapGVar composes an additional projection (any InterpretOp instance, including the built-in Op) onto an existing GVar, the analogue of quickcheck-lockstep's mapGVar.
• Four test entry points: lockstepProperty, lockstepPropertyWith, lockstepParallel, and lockstepParallelWith.
• Monad-parameterized variants lockstepPropertyM, lockstepPropertyWithM, lockstepParallelM, and lockstepParallelWithM accepting a forall a. m a -> PropertyT IO a (or env -> m a -> PropertyT IO a) natural transformation. Lets users write commands in a custom monad stack (e.g., ReaderT env (PropertyT IO)) and supply the runner separately, without hardcoding PropertyT IO into every lsCmdExec.
• hoistLockstepCmd :: (forall a. m a -> n a) -> LockstepCmd m model -> LockstepCmd n model for retargeting a command's monad.
• New module Hedgehog.Lockstep.Observe exposing an Observation GADT (ObserveEq, ObserveProject, ObservePair, ObserveCustom) and runObservation. The GADT factors out the common model-output-versus-real-output comparison patterns into a typed DSL so users can write lsCmdObserve = runObservation ObserveEq or lsCmdObserve = runObservation (ObserveProject normM normR) instead of writing the assertion by hand. This is the hedgehog-lockstep analogue of quickcheck-lockstep's Observable/ModelValue split.
• New module Hedgehog.Lockstep.Examples exposing lockstepLabelledExamples, a model-only driver that samples random command sequences, accumulates the tags emitted by lsCmdTag, and prints one shortest sampled trace per tag. This is the analogue of QuickCheck's labelledExamples and quickcheck-lockstep's tagActions: it answers "is the generator actually hitting the labelled cases I expect" without running the real system at all. The accompanying LabelledExamples summary type and ModelStep trace entry are exposed for callers that want to inspect the sampled traces directly.
• lockstepCommands for users who want to drive Gen.sequential / executeSequential directly.
• README guidance and a Test.KVStore example for using Hedgehog.label / classify inside lsCmdObserve for coverage labels.
• lsCmdInvariants :: model -> output -> Test () field on LockstepCmd for system invariants that should hold after every command, separate from the lockstep equality check in lsCmdObserve.
• lsCmdTag :: model -> model -> modelOutput -> [String] field on LockstepCmd for per-step coverage tagging. Receives the pre- and post-step model and the model's predicted output; each returned tag is reported via Hedgehog.label. This is the analogue of quickcheck-lockstep's tagStep and is the natural place for tags whose value depends on how the model state changed during the step.
• Per-step model-state footnote: toLockstepCommand adds a footnote of the post-step model after every command. Hedgehog only displays footnotes on test failure, so passing tests are unaffected; on failure the model-state evolution shows alongside the shrunken command sequence (analogue of quickcheck-lockstep's monitoring counterexample enrichment).
• Module-level Haddock for every public module, plus disambiguated identifier references so Haddock builds cleanly with no warnings.
• README caveat documenting the dependency on Hedgehog.Internal.State.
• Test.UnitCoverage exercising applyOp, gvarLabel, mapGVar, and mkGVarId.
• InterpretOp class with interpretOp :: op a b -> a -> Maybe b. mkGVar and mapGVar accept any op type with InterpretOp and Show instances, not just the built-in Op. Users can extend the projection vocabulary (e.g., a list-head op) by defining their own GADT and supplying instances. The built-in Op is itself an instance of InterpretOp, and applyOp is exported as a synonym for interpretOp. This is the analogue of quickcheck-lockstep's Operation/InterpretOp classes, closing the structural-flexibility gap with that library.
• Test.CustomOp exercising a user-defined op (MyOpHead :: MyOp [a] a) end-to-end through a real lockstep test.