Testing and Golden Artifacts

• Golden tests compare serialized AST JSON for fixtures under tests/fixtures/*.pml and goldens in tests/golden/*.json.
• Regenerate goldens only via environment switch:

UPDATE_GOLDEN=1 cargo test -p proofdown_parser

• Parser limits and error-path tests ensure safe failures with structured errors.
• Validator unit tests enforce attribute bounds and whitelist behavior.
• Fuzzing and property tests ensure robustness on adversarial inputs.