Create or refactor Foundry deployment fixtures for Solidity tests. Use when Codex needs to separate Deploy.t.sol, BaseTest.t.sol, BaseFuzzTest.t.sol, deployment scripts, shared actors, token funding, approvals, and reusable fuzz bounds before adding unit, fuzz, property, or differential tests.
Create Foundry differential tests comparing production Solidity contracts against an independent reference model. Use when Codex needs paired deployments, paired actions, public-view state comparisons, strict equality checks, and root-cause classification of production/reference divergence.
Classify failing Foundry fuzz, property, invariant, and differential tests. Use when Codex needs to run forge tests, reproduce counterexamples, spawn fresh investigations, separate harness defects from reference bugs and production bugs, and report strict-equality failures without masking them.
Create Foundry fuzz tests from deterministic unit tests. Use when Codex needs to mirror unit-test flows as parametric fuzz tests, add bounded inputs, expected-vs-actual assertions, quote/execution checks, exact-in/out cases, partial fills, and rounding-sensitive tests without changing production contracts.
Build a simple independent Solidity reference implementation for Foundry tests. Use when Codex needs a non-optimized, non-production-derived model for differential testing, based only on public interfaces, specs, README/API docs, and existing public tests.
Audit a Solidity reference implementation against a protocol whitepaper or public specification. Use when Codex needs to decide whether reference-model behavior, math, edge cases, or unsupported surfaces match the spec before creating or trusting Foundry differential tests.
Turn whitepapers, protocol specs, and public documentation into Foundry property tests. Use when Codex needs to derive invariants, conservation rules, atomicity rules, priority rules, price-view behavior, or accounting properties from external specs without weakening tests that expose production mismatches.
Master skill for running an end-to-end multi-pass Foundry testing campaign for Solidity projects. Use when Codex needs to create a goal and coordinate fixture setup, fuzz tests, spec properties, reference implementations, differential tests, and independent failure triage until the testing objective is genuinely complete.