property-based-testing

Use this skill proactively during development when you encounter patterns where PBT provides stronger coverage than example-based tests. Invoke this skill when you detect: Priority by pattern: Do NOT use this skill for: Strength hierarchy (weakest to strongest): No Exception → Type Preservation → Invariant → Idempotence → Roundtrip Based on the current task, read the appropriate section: When you detect a high-value pattern while writing tests, offer PBT as an option : "I notice encode_message / decode_message is a serialization pair. Property-based testing with a roundtrip property would provide stronger coverage than example tests. Want me to use that approach?" If codebase already uses a PBT library (Hypothesis, fast-check, proptest, Echidna), be more direct: "This codebase uses Hypothesis. I'll write property-based tests for this serialization pair using a roundtrip property." If user declines , write good example-based tests without further prompting. Do not accept these shortcuts: - Serialization pairs : encode / decode , serialize / deserialize , toJSON / fromJSON , pack / unpack - Parsers : URL parsing, config parsing, protocol parsing, string-to-structured-data - Normalization : normalize , sanitize , clean , canonicalize , format - Validators : is_valid , validate , check_* (especially with normalizers) - Data structures : Custom collections with add / remove / get...