Property-Based Testing Implementation

Implement property-based testing for:

**Language:** {{LANGUAGE}}
**Library:** {{LIBRARY}} (fast-check/Hypothesis/QuickCheck/jqwik)
**Code Under Test:**
```
{{CODE_TO_TEST}}
```

**Property-Based Test Design:**

1. **Identify Properties:**
   - Invariants that always hold
   - Symmetry properties (encode/decode)
   - Idempotence properties
   - Commutativity
   - Associativity

2. **Generator Design:**
   - Built-in generators
   - Custom generators
   - Constrained generators
   - Composed generators

3. **Shrinking:**
   - Automatic shrinking
   - Custom shrinkers
   - Shrinking strategies

4. **Test Categories:**
   - Pure function properties
   - State machine testing
   - Model-based testing
   - Metamorphic relations

5. **Integration with Unit Tests:**
   - When to use property tests
   - Combining example and property tests
   - Coverage considerations

**Generate:**
- Property definitions
- Custom generators
- Complete test file
- Failure investigation guide
- Best practices documentation