test(fuzz): Contract Mutation & Adversarial Fault Injection Testing Suite

[sdageltc]

Summary & Motivation

To guarantee that letitloop remains mathematically indestructible against rogue workers, file system corruptions, and flaky external commands, we want to build a formal Adversarial Fault Injection & Mutation Testing Suite.

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Proposed Fault Injection Scenarios

1. Out-of-Bounds File Mutation:
   • A mock worker attempts to modify files in parent directories (../../etc/passwd or ../sibling_module). Verifies scope.py blocks/detects the violation 100% of the time.
2. Zombie Process Leakage:
   • A mock worker forks child background processes that refuse SIGTERM. Verifies supervisor cleans them up.
3. Simulated State Journal Corruption:
   • Injects truncated JSON or random byte noise into journal.jsonl mid-turn. Verifies apply_checkpoint and WAL recovery reconstruct valid state without crashing.
4. Deterministic Infinite Loop Simulation:
   • A mock worker produces identical non-divergent outputs across retries. Verifies failure.py 3-strike impossibility triggers deterministically on Strike 3.

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Acceptance Criteria

• All fault injection suites execute under 5 seconds with zero external dependencies.
• 100% test pass rate demonstrating resilient fail-closed behavior.