Your Fuzzer Is Only as Smart as Its Oracle

Short summary

A schema migration test passed despite having a catastrophic path that would drop production data. The core insight: your fuzzer is only as smart as its oracle—what you test for, not how many cases you run. Instead of building reference implementations, use property-based laws (convergence, idempotency, rollback, safety) to verify invariant relations, letting AI cheap out the harness infrastructure while you focus on defining what "correct" means.

• •Testing catastrophic-but-correct migrations requires checking both the destination AND the path
• •Oracles (what you verify) matter infinitely more than generators (how many cases you try)
• •Property-based testing with semantic laws beats reference-implementation diffing for most tools

Generated with AI, which can make mistakes.