Property-Based Testing Strategy (Hypothesis)

Goal

Stop hand-picking a few example inputs and instead state the properties that must hold for all inputs, then let Hypothesis generate hundreds of diverse cases to attack them. A property-based test asserts an invariant ("the output is always sorted", "decode(encode(x)) == x") rather than a single example. When it finds a failure, Hypothesis shrinks the counterexample to the smallest input that still breaks the property, handing you a minimal reproduction. The output of this skill is a property test plan: the invariants you will check, the strategies that generate inputs for them, and — for stateful systems — the state machine that drives them. Be clear from the start: PBT samples the input space to raise confidence; it does not enumerate it and does not prove correctness.