What problem does it solve? Example-based tests only check hand-picked inputs, leaving most of the input domain untested and letting edge-case bugs slip through. This Skill helps you assert rules over entire input domains so generators hunt for counterexamples, and it helps you tell a real bug from a wrong property when a test fails. ## Core Features & Use Cases - Property identification and test writing: Apply a catalog of properties (roundtrip, inverse, oracle, idempotence, invariants) with strategy design, edge-case pinning, and correct settings for Hypothesis, fast-check, proptest, jqwik, rapid, and more. - Test review and failure triage: Detect tautological, vacuous, and reimplementing tests, then classify shrunk counterexamples as code bugs, wrong properties, or ambiguous specs. - Smart contract invariants: Write Echidna and Medusa property-mode and assertion-mode tests for Solidity, covering solvency, supply conservation, and access control. - Use Case: Given a URL canonicalizer, generate a Hypothesis suite that discovers a percent-encoding defect where a second pass re-encodes its own escapes, then verify the suite fails on the defective code and passes on the patched version. ## Quick Start Ask the assistant to write property-based tests for your serializer, parser, or validator, or to review an existing Hypothesis or fast-check suite for weak assertions.
