Testing & Tooling

Unit testing modules

Each module should have focused Foundry tests that call the hook functions directly. Example for the whitelist policy:

contract WhitelistModuleTest is Test {
    WhitelistModule module;
    address constant AGGREGATOR = address(0xA11CE);

    function setUp() public {
        module = new WhitelistModule(AGGREGATOR);
    }

    function testBlocksUnknownAddress() public {
        vm.expectRevert(WhitelistModule.NotWhitelisted.selector);
        module.beforeSwap(IPoolManager(address(0)), address(1), key, params, bytes(""));
    }
}

Because the module checks msg.sender, be sure to vm.prank(AGGREGATOR) when invoking hooks.

Integration testing with MODL

Use mocks for IPoolManager to simulate Uniswap callbacks. The repo includes test/MODLAggregator.t.sol, which you can extend:

function test_whitelist_blocks_non_whitelisted() public {
    MODLAggregator.ModuleConfigInput[] memory configs = _basicConfig();
    aggregator.setModules(configs);

    vm.expectRevert(abi.encodeWithSelector(
        MODLAggregator.ModuleExecutionFailed.selector,
        address(whitelist),
        MODLAggregator.Hook.BeforeSwap,
        abi.encodeWithSelector(WhitelistModule.AddressNotWhitelisted.selector, trader)
    ));

    manager.callBeforeSwap(aggregator, trader, poolKey, params, bytes(""));
}

Gas reports

forge test --gas-report shows per-function costs, helping you choose gas limits. Run it on both modules and the aggregator integration tests to spot regressions.

Tooling tips

• Script deployments – Foundry script/ files can deploy modules, register them, and configure routes in one transaction.
• Static analysis – Use slither or sforge to ensure modules don't have reentrancy holes or unchecked external calls.
• Snapshots – When you update module ordering, snapshot _modules via getModules() and compare to previous deployments to verify priorities.
• Scaffolding – Use @modl/cli (modl init, modl module:new ...) to generate modules/tests from templates before adding your custom logic.

An automated test suite that mixes module-level and aggregator-level checks is the best defense against regressions when composing many behaviors.