fork-test

Fork Test Skill

Generate Foundry fork tests for a specific contract, validating behavior against real on-chain state. Fork tests complement unit tests for paths that mocks cannot faithfully reproduce — AMO pool interactions, real router swaps, oracle reads, gauge rewards, and cross-chain flows. Follow the guidelines below to ensure consistency and maintainability across our fork test suite.

1. Directory Layout

contracts/tests/fork/<category>/<ContractName>/
├── shared/
│   └── Shared.t.sol          # Abstract base with setUp, fork creation, deploy, helpers
└── concrete/
    ├── Deposit.t.sol          # One file per integration scenario
    ├── Withdraw.t.sol
    └── Rebalance.t.sol

NEVER fuzz/ directory — fork tests are concrete only (RPC calls make fuzz runs prohibitively slow).

Fewer files than unit tests: Only create files for functions with meaningful integration behavior (pool interactions, swaps, bridge flows). Simple setters, view functions, and access control are covered by unit tests.

<category> matches the subdirectories already in contracts/tests/fork/ (strategies, vault, token, etc.).

One file per integration scenario

Each file tests one public/external function's interaction with real on-chain state. The file name uses PascalCase matching the function name (e.g. deposit() → Deposit.t.sol).

Do NOT create fork test files for:

• Functions already fully covered by unit tests with no external protocol dependency
• Simple setters, view functions, access control, constructor validation, pure math

2. Inheritance Chain

forge-std/Test
  └─ Base  (contracts/tests/Base.t.sol)  — actors, constants, fork IDs, contract refs
       └─ BaseFork  (contracts/tests/fork/BaseFork.t.sol)  — fork creation helpers
            └─ Fork_<Contract>_Shared_Test  (shared/Shared.t.sol)  — abstract; setUp, deploy, helpers
                 └─ Fork_Concrete_<Contract>_<Feature>_Test  (concrete/*.t.sol)

• Base creates actors (alice, bobby, …, governor, strategist, etc.) and declares constants, IERC20 external token refs, and fork IDs (forkIdMainnet, forkIdBase, forkIdSonic, forkIdArbitrum). Base only contains actors, constants, IERC20 external tokens, fork IDs, and setUp(). All typed contract/proxy/mock state variables are declared in each Shared.t.sol file.
• BaseFork provides _createAndSelectFork<Chain>() helpers that read RPC URLs from environment variables and create Foundry forks.
• Fork_<Contract>_Shared_Test is abstract and owns all deployment + configuration logic on top of the fork.
• Concrete test contracts inherit Fork_<Contract>_Shared_Test directly — no extra layers.