Fixtures

Fixtures are the contract every implementation of the judge must satisfy. They are Prolog facts so that any implementation can load them without a second parser.

Verdict fixtures (`verdicts/`)

verdict(Id, Backend, Profiles, Term, Expected).

• Id: atom, unique across all files, prefixed by file (core_unbound_call).
• Backend: iso | swi | scryer | trealla. Fixtures under iso run on every engine in CI.
• Profiles: list of profile names in force.
• Term: the goal or clause, as a term (not text; reader fixtures cover text).
• Expected: admit | admit_with(Rewrites) | admit_needs(Profiles) | refused(Class, Rule). Rule may carry depth(N).

  A fixture that is refused under profiles P must also be refused under every subset of P (monotonicity). A rewrite must be admitted under exactly the profiles the original is admitted under. CI checks both.

Reader fixtures (`reader/`)

reader(Id, Backend, Text, Canonical).

Text is author input as an atom. Canonical is the operator-free canonical form the Hornguard reader must produce, and the form the backend engine's own reader must also produce from Text. Disagreement is a failing fixture. refused(reader(Reason)) in place of Canonical marks text the reader must refuse (quasi-quotations, operator tricks, confusables, pathological depth).

Detection fixtures

Every refused(Class, Rule) fixture is also a detection fixture: a change that still refuses the term but reclassifies it fails CI. Silent reclassification is the regression that is otherwise invisible.

Growing the suite

Every externally reported escape becomes a fixture before its fix lands.