Property-Based Testing

Use generated inputs to search for unknown counterexamples to behavior that should hold across many inputs.

Example-based tests confirm known scenarios. Property-based tests search for unknown failures of a stated property.

Guard Condition

Before recommending or writing a property-based test, state:

1. The property that should hold.
2. The generated input or action space.
3. The unknown counterexample class this test may expose.
4. The oracle: how the test knows the behavior is wrong.

If any item is missing, use example-based tests instead.

Do not invoke this skill merely because the code involves permissions, state machines, parsers, serializers, migrations, or another broad-input domain. Those domains are common fits only when a concrete property can be named: