What problem does it solve? Example-based unit tests only cover the inputs you think of, leaving parsers, converters, and codecs exposed to panics and edge cases on unexpected data. This Skill guides you through property-based testing with hegel, Antithesis's Hypothesis-based Rust library, so generated inputs, automatic shrinking, and failure replay find real counterexamples for you. ## Core Features & Use Cases - Property Selection Guidance: Prioritizes high-value properties such as never-panics, round-trip, determinism, idempotence, and model-based comparison against a reference implementation. - Generator Patterns: Covers recursive structures with gs::deferred, bounded vectors with max_size, composite generators, and keeping generated programs well-formed by construction. - Budget, Replay, and CI Determinism: Explains test_cases budgets, the .hegel failure database, and how to convert shrunk counterexamples into regression tests for CI. - Use Case: When fuzzing a Nix-to-TypeScript transpiler, generate well-formed source, assert the output parses under an independent parser like rnix, and let hegel shrink any failure to a minimal case you copy into a regression test. ## Quick Start Add property-based tests to my Rust parser crate using hegel so it never panics on arbitrary text input.
