Foundry development environment setup

Foundry Development Environment Setup

Foundry is a Rust-based toolchain for smart contract development: Forge (tests and compilation), Cast (chain interaction), Anvil (local node), Chisel (Solidity REPL). It outperforms Hardhat in compilation speed and test execution by 10-50x on typical projects.

Installation and Basic Configuration

curl -L https://foundry.paradigm.xyz | bash
foundryup  # install/update to latest version

Structure of a new project (forge init my-project):

my-project/
├── foundry.toml       # main config
├── src/               # contracts
├── test/              # tests (.t.sol)
├── script/            # deployment scripts (.s.sol)
└── lib/               # dependencies (git submodules)

foundry.toml — compiler and test configuration:

[profile.default]
src = "src"
out = "out"
libs = ["lib"]
solc = "0.8.24"
optimizer = true
optimizer_runs = 200
via_ir = false        # enable for complex contracts with Stack too deep
fuzz = { runs = 1000 }
invariant = { runs = 256, depth = 500 }

[profile.ci]
fuzz = { runs = 10000 }
invariant = { runs = 1000, depth = 1000 }

Separate [profile.ci] allows running heavier fuzzing in CI without slowing local development.

Dependencies via forge install

forge install OpenZeppelin/openzeppelin-contracts
forge install foundry-rs/forge-std

Dependencies are git submodules in lib/. Remappings in foundry.toml:

remappings = [
    "@openzeppelin/=lib/openzeppelin-contracts/",
    "forge-std/=lib/forge-std/src/",
]

Anvil — Local Node

# Run with mainnet fork
anvil --fork-url $MAINNET_RPC --fork-block-number 19000000 --chain-id 1

# With pre-configured accounts and balances
anvil --accounts 10 --balance 1000

Fork mainnet — key feature for testing integrations. Contract interacts with real Uniswap, Aave, Chainlink — no mocks, on real chain state at a specific block.

Fuzz and Invariant Tests

Foundry fuzzing works out of the box — just declare a function parameter:

function testFuzz_Deposit(uint256 amount) public {
    amount = bound(amount, 1, 1e27); // limit range
    token.mint(alice, amount);
    vm.prank(alice);
    vault.deposit(amount);
    assertEq(vault.balanceOf(alice), amount);
}

Invariant tests verify system invariants after arbitrary sequences of calls:

function invariant_TotalSupplyEqualsDeposits() public {
    assertEq(vault.totalSupply(), vault.totalDeposits());
}

It's exactly an invariant test that finds in 20 minutes an edge case that manual tests missed: at a specific sequence of deposit → withdraw → deposit with specific amounts, totalSupply diverged by 1 wei due to rounding.

CI Integration (GitHub Actions)

- name: Install Foundry
  uses: foundry-rs/foundry-toolchain@v1

- name: Run tests
  run: forge test --profile ci -v
  env:
    FOUNDRY_ETH_RPC_URL: ${{ secrets.MAINNET_RPC }}

Timeline

Setting up Foundry with dependencies, profile configuration and CI integration: 2-3 hours for a standard project. If fork testing setup with specific protocols and writing basic invariant tests is needed — up to one day.

Cost is calculated individually.