Utilities

The ModuleKit comes with a some additional utilities to help you test your modules and ensure that they behave as expected.

Gas Calulations

The ModuleKit comes with a gas testing helper library to test gas consumption of UserOps, including for the different phases of the ERC-4337 flow and L2-L1 calldata gas.

Setup

Before using this utility, create a folder called gas_calculations in the root folder of the directory (same level as the src folder) and ensure that you have the right permissions settings set in your foundry.toml file:

fs_permissions = [{ access = "read-write", path = "gas_calculations" }]

Usage

In order to use the gas testing utility, follow the steps below:

1. In the test function(s) that you want to perform, call instance.log4337Gas("identifier") before a UserOperation is executed. This will log the gas used for the UserOperation and use the identifier as the filename for the gas report. Make sure to use a unique identifier for each UserOp, otherwise the gas reports will be overwritten.

2. Execute your tests and add GAS=true to the start of the command. For example: GAS=true forge test.

3. After the tests have finished, the gas reports will be written to the gas_calculations folder in the root of the project. A gas report will look like this:

{
  "Calldata": {
    "Arbitrum": "6504 gas",
    "OP-Stack": "8859 gas"
  },
  "Phases": {
    "Creation": "187_170 gas",
    "Execution": "37_054 gas",
    "Validation": "35_980 gas"
  },
  "Total": "2_550_948 gas"
}

Note that if you re-run gas calculations, then the newest number will be added and every value will be followed by a (diff: ...) that shows the difference, in gas units between the calculations.

4. All numbers are in gas units. To calculate the cost in gwei, follow the instructions below:

• On L1: multiply the total gas used by the gas price in gwei: totalGasUsed * gasPrice
• On an L2: multiply the total gas used by the L2 gas price in gwei and then add it to to the result of the relevant L2-L1 gas cost muliplied by the L1 gas cost in gwei: totalGasUsed * l2GasPrice + callDataGasUsed * l1GasPrice

Note: if you are calculating the dollar amount of the gas cost, make sure to use the relevant gwei to usd conversions if the L2 has a different gas token to L1.

ERC-4337 Restrictions

ModuleKit allows you to test whether your modules adhere to the ERC-4337 restrictions. These restrictions only apply to the validation phase, so only Validators will need to adhere to them (read more).

In order to simulate these restrictions, simply add SIMULATE=true before your test command. For example: SIMULATE=true forge test. If any of the tests violate any of the ERC-4337 Restrictions, then the ModuleKit will throw an error and describe which restriction has been violated.