Fork Test

Generate Foundry fork tests for contracts whose behavior depends on real on-chain state, live liquidity, routers, gauges, or oracle reads.

1. Directory layout

contracts/tests/fork/<category>/<ContractName>/
├── shared/
│   └── Shared.t.sol
└── concrete/
    ├── Deposit.t.sol
    ├── Withdraw.t.sol
    └── Rebalance.t.sol

Rules:

• fork tests are concrete only; do not add a fuzz/ directory
• create files only for functions with meaningful on-chain integration behavior
• keep simple setters, access control checks, and pure validation in unit tests

2. Inheritance chain

forge-std/Test
  └─ Base
       └─ BaseFork
            └─ Fork_<Contract>_Shared_Test
                 └─ Fork_Concrete_<Contract>_<Feature>_Test

Base owns shared actors, constants, IERC20 external token refs, and fork IDs. All typed contract/proxy/mock state variables are declared in each Shared.t.sol using interface types. BaseFork owns chain fork helpers.

Interface-only testing

Same rules as unit tests — use interfaces, not concrete contracts:

• Import interfaces: IVault, IOToken, IProxy, strategy interfaces from contracts/interfaces/strategies/
• Deploy fresh contracts with vm.deployCode instead of new (except mocks), and always reference artifact paths through tests/utils/Artifacts.sol (e.g. vm.deployCode(Vaults.OETH, abi.encode(address(weth)))); add the entry to the relevant sub-library if it does not exist yet
• Cast forked addresses to interfaces: oethVault = IVault(Mainnet.OETH_VAULT)
• Reference events from interfaces: emit IVault.EventName(...)

Product-specific vault types

Product	Token	Vault	Chain	Artifacts reference
OUSD	OUSD	OUSDVault	Mainnet	Vaults.OUSD
OETH	OETH	OETHVault	Mainnet	Vaults.OETH
OETHBase	OETHBase	OETHBaseVault	Base	Vaults.OETH_BASE

Add the entry to tests/utils/Artifacts.sol if it does not exist yet.

3. Shared setup contract

shared/Shared.t.sol should keep setup in this order:

function setUp() public virtual override {
    super.setUp();
    _createAndSelectFork<Chain>();
    _deployFreshContracts();
    _configureContracts();
    label();
}

Decision rule:

• deploy fresh contracts that the strategy or vault under test owns or manages
• use forked addresses for external infrastructure such as routers, tokens, factories, and oracles

Pull canonical addresses from tests/utils/Addresses.sol.

4. Concrete test naming

File and contract naming:

concrete/Deposit.t.sol
Fork_Concrete_<ContractName>_Deposit_Test

Function naming patterns:

• test_<function>()
• test_<function>_<behavior>()
• test_<function>_RevertWhen_<condition>()
• test_<function>_emits<EventName>()

Casing rules:

• function, behavior, and condition stay camelCase
• RevertWhen is the only PascalCase token in the test name

5. What belongs in fork tests

Fork-test these categories:

• AMO pool interactions
• real router swaps
• oracle reads
• gauge reward flows
• cross-chain and bridge flows
• vault rebases with real balances
• zapper flows
• multi-step end-to-end operations

Do not fork-test:

• simple setters
• straightforward view functions
• access control checks
• constructor validation
• pure math and helper logic
• input-validation-only reverts

Litmus test:

If a mock can faithfully reproduce the behavior, keep it in unit tests.

6. Chain mapping

Use the repository's fork helpers and address libraries consistently:

• Mainnet -> _createAndSelectForkMainnet()
• Base -> _createAndSelectForkBase()
• Arbitrum if relevant -> _createAndSelectForkArbitrum()

Output expectations

When implementing fork tests:

• keep them narrowly focused on real integration value
• prefer a few strong end-to-end tests over broad but redundant coverage
• label both fresh and forked contracts for readable traces
• use interface-only imports; no concrete contract imports except mocks
• deploy fresh contracts with vm.deployCode, not new (mocks are fine with new), and reference all artifact paths through tests/utils/Artifacts.sol — no inline "contracts/...sol:Name" strings
• mirror existing fork test structure in the nearest comparable test suite before introducing a new pattern