Foundry

Overview of the Foundry Smart Contract Development Toolkit

Introduction

Foundry is an alternative to tools like Hardhat, Truffle, Brownie, etc.

There are two main flaws with tools like Hardhat, Truffle, and Brownie:

  1. They require the use of another language like JavaScript or Python for writing scripts.

  2. They are slow.

Foundry is the superior choice is because:

  1. Scripts and tests can be written in Solidity, the same language we use to write Ethereum smart contracts.

  2. There is a wide array of CLI commands that aid in smart contract development, testing, deployment, as well as EVM chain interaction.

  3. Foundry is incredibly fast because it was written in Rust.

Official Links

📖 Foundry Book (Docs)

⚙️ Foundry Github

Solidity Compiler Management

Foundry relies on svm-rs to install and detect Solidity compiler versions. Working on multiple projects may require using different solc versions.

For a guide on how to manage solc versions, please refer to the Solidity Compiler section of these notes.

Forge Commands

The forge command is used to build, test, and deploy smart contracts.

Compile a Contract

  • Foundry Book - forge build

  • The following command will compile all contracts inside the /src directory and save the output in the /out directory.

forge build

Deploy a Contract

  • Foundry Book - forge create

  • The --etherscan-api-key <API_KEY> --verify part is only required if you would like your contract to be automatically verified on the chain's block explorer, which is highly recommended. You can get an API key by creating an account on the chain's block explorer (e.g., Etherscan, Arbiscan, Polygonscan, etc.).

forge create <CONTRACT_FILE_PATH>:<CONTRACT_NAME> --constructor-args <ARG1> <ARG2> --rpc-url <RPC_URL> --private-key <PRIVATE_KEY> --etherscan-api-key <API_KEY> --verify

Run a Specific Unit Test

  • Foundry Book - forge test

  • The following command assumes that the unit test will be running on a forked network.

  • The -vvvvv flag specifies the level of verbosity (i.e., how much detail to display in the terminal as the test runs). In this case, we are specifying the highest level (Level 5). If we don't specify this flag, Level 1 is assumed, -vv = Level 2, -vvv = Level 3, etc.

forge test --fork-url <RPC_URL> --match-test <TEST_NAME> -vvvvv

Run All Unit Tests

  • Foundry Book - forge test

  • The following command assumes that the unit test will be running on a forked network.

  • Also, the minimum amount of detail will be displayed in the terminal as the tests run, since the default verbosity is Level 1.

forge test --fork-url <RPC_URL>

Cast Commands

The cast command is used to perform Ethereum RPC calls to deployed smart contracts.

Call a Function

  • Foundry Book - cast call

  • Calling a contract function does not modify any on-chain data. This is simply a way to read data returned by the function that we call using the cast call command.

cast call <CONTRACT_ADDRESS> "functionName(<PARAM1_TYPE>, <PARAM2_TYPE>)" <PARAM1> <PARAM2> --rpc-url <RPC_URL>

Submit a Transaction

  • Foundry Book - cast send

  • Submitting a transaction to a contract function will modify on-chain data. In order to successfully do this, we need to sign the transaction with our private key and pay the corresponding gas fee.

cast send <CONTRACT_ADDRESS> "functionName(<PARAM1_TYPE>, <PARAM2_TYPE>)(<RETURNED_VALUE_TYPE>)" <PARAM1> <PARAM2> --rpc-url <RPC_URL> --private-key <PRIVATE_KEY>

Send Native Token to Account

The amount can be an integer, which defaults to Wei, or you can specify the units. For example 1ether.

cast send <SOME_ADDRESS> --value <AMOUNT> --private-key <PRIVATE_KEY>

Convert a UTF-8 String to Hexadecimal

cast from-utf8 "hello world"

Get Keccak-256 Hash of a custom Smart Contract Error

cast keccak "InsufficientFunds()" | cut -c1-10

Generate the ABI-Encoded Calldata for a Smart Contract Function Call

cast calldata "somFunc(address,uint256)" <ADDRESS_ARG> <UINT_ARG>

Testing on Local Mainnet Fork

Create a Local Fork

The anvil command is used to create a local Mainnet fork for deploying and testing smart contracts.

Foundry Book - anvil reference

  • The --chain-id and --port commands are optional.

  • If --chain-id is not specified, the default value is set to it's Mainnet counterpart (i.e., chain ID would be 1 for Ethereum).

  • If --port is not specified, the default value is set to 8545.

anvil --fork-url <RPC_URL> --chain-id <CHAIN_ID> --port <PORT>

Impersonate an Account

This allows you to submit transactions as if you were the owner of the account you are impersonating.

cast rpc anvil_impersonateAccount <SOME_ADDRESS>

Transfer ERC-20 Balance from Impersonated Account

After impersonating an account with a significant balance of some ERC-20 token, the following command allows you to transfer that balance to some recipient account.

cast send <ERC20_ADDRESS> --from <IMPERSONATED_ADDRESS> "transfer(address,uint256)(bool)" <RECIPIENT> $(cast call <ERC20_ADDRESS> "balanceOf(address)(uint256)" <IMPERSONATED_ADDRESS>) --unlocked

Common Errors

code 128

When installing git submodules using forge install, the installation may fail with the error git submodule exited with code 128. This is typically due to initiating the project's git repository without using forge init.

To get around this, do the following:

forge install $SUBMODULE_URL --no-commit
git add -A
git commit -m "forge install: sumboduleName"
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