Foundry Setup Skill

This skill provides templates, scripts, and best practices for setting up Foundry-based Solidity projects.

When to Use

Use this skill when:

• Initializing a new Foundry project
• Adding Foundry to an existing Solidity codebase
• Configuring Foundry settings (optimization, tests, etc.)
• Setting up Foundry in a hybrid Hardhat/Foundry project
• Updating Foundry configuration

Prerequisites: Foundry must be installed (foundryup)

Integration with Framework Detection

Before using this skill, reference the framework-detection skill to:

• Check if Foundry is already configured
• Determine if this is a hybrid setup
• Avoid overwriting existing configuration

Quick Setup

Basic Initialization

# Initialize new Foundry project
forge init my-project
cd my-project

# Or initialize in existing directory
forge init --force

Project Structure

Foundry creates this structure:

project/
├── foundry.toml          # Configuration
├── .env.example          # Environment variables template
├── lib/                  # Dependencies (git submodules)
├── src/                  # Contract source files
│   ├── interfaces        # Interfaces
│   │   └──ICounter       # Example interface
│   └── Counter.sol       # Example contract
├── test/                 # Test files
│   └── Counter.t.sol     # Example test
└── script/               # Deployment scripts
    └── Counter.s.sol     # Example script

Configuration Templates

foundry.toml

See ./templates/foundry.toml for the complete configuration template.

Key Configuration Sections:

[profile.default]
src = "src"
out = "out"
libs = ["lib"]
solc_version = "0.8.30"
optimizer = true
optimizer_runs = 200
via_ir = false

# Testing
verbosity = 2
fuzz_runs = 256

# Gas reporting
gas_reports = ["*"]

# Formatting
line_length = 120
tab_width = 4
bracket_spacing = false

Environment Variables

See ./templates/.env.example for complete environment variable template.

Essential Variables:

# RPC URLs
MAINNET_RPC_URL=
SEPOLIA_RPC_URL=
ARBITRUM_RPC_URL=

# Private Keys (NEVER commit actual keys)
PRIVATE_KEY=

# Etherscan API Keys
ETHERSCAN_API_KEY=
ARBISCAN_API_KEY=

# Gas Price Settings
GAS_PRICE=

Common Configurations

1. High Optimization for Production

[profile.production]
optimizer = true
optimizer_runs = 10000
via_ir = true

2. Detailed Testing

[profile.test]
verbosity = 3
fuzz_runs = 1000
invariant_runs = 256

3. Gas Optimization Focus

[profile.gas-optimized]
optimizer = true
optimizer_runs = 1000000
via_ir = true
gas_reports = ["*"]

4. Mainnet Forking for Tests

[profile.default]
fork_url = "${MAINNET_RPC_URL}"
fork_block_number = 18000000

Dependencies Management

Adding Libraries

# Add OpenZeppelin contracts
forge install OpenZeppelin/openzeppelin-contracts

# Add Solmate
forge install transmissions11/solmate

# Add Forge Standard Library (included by default)
forge install foundry-rs/forge-std

Remappings

Foundry auto-generates remappings.txt, but you can customize:

@openzeppelin/=lib/openzeppelin-contracts/
@solmate/=lib/solmate/src/
forge-std/=lib/forge-std/src/

Or configure in foundry.toml:

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

Initialization Script

See ./scripts/init-foundry.sh for automated setup.

Usage:

# Basic initialization
./scripts/init-foundry.sh

# With project name
./scripts/init-foundry.sh my-project

# In existing directory
./scripts/init-foundry.sh --force

What the script does:

1. Checks if Foundry is installed
2. Initializes Foundry project
3. Copies configuration templates
4. Sets up .gitignore
5. Installs essential dependencies
6. Creates initial directory structure

Hybrid Setup (Foundry + Hardhat)

When adding Foundry to an existing Hardhat project:

1. Initialize Foundry Without Overwriting

# Initialize but don't overwrite existing files
forge init --no-commit

2. Configure Separate Directories

# foundry.toml
[profile.default]
src = "contracts"          # Use Hardhat's contracts dir
test = "test/foundry"      # Separate Foundry tests
out = "out"
libs = ["node_modules", "lib"]  # Include both package managers

3. Update .gitignore

# Foundry
out/
cache/
lib/

# Hardhat
artifacts/
cache/
node_modules/

4. Install Shared Dependencies

# Install via Foundry
forge install OpenZeppelin/openzeppelin-contracts

# Reference in Hardhat
# Add to hardhat.config.js:
# paths: { sources: "./contracts" }

Testing Setup

Basic Test Structure

// SPDX-License-Identifier: MIT
pragma solidity ^0.8.30;

import "forge-std/Test.sol";
import "../src/MyContract.sol";

contract MyContractTest is Test {
    MyContract public myContract;

    function setUp() public {
        myContract = new MyContract();
    }

    function testBasic() public {
        // Test implementation
    }

    function testFuzz_Amount(uint256 amount) public {
        // Fuzz test
    }
}

Running Tests

# Run all tests
forge test

# Run specific test
forge test --match-test testBasic

# Run with verbosity
forge test -vvvv

# Run with gas reporting
forge test --gas-report

# Run with coverage
forge coverage

Security Best Practices for Private Keys

⚠️ CRITICAL: Never store production private keys in .env files!

Recommended Approaches (in order of preference)

1. Hardware Wallets (Most Secure - Production)

# Deploy using Ledger
forge script script/Deploy.s.sol:DeployScript \
  --rpc-url $RPC_URL \
  --ledger \
  --broadcast

# Deploy using Trezor
forge script script/Deploy.s.sol:DeployScript \
  --rpc-url $RPC_URL \
  --trezor \
  --broadcast

2. Cast Wallet (Recommended - Development & Production)

Create a named keystore:

# Create a new wallet (prompts for password)
cast wallet new ~/.foundry/keystores/deployer

# Import existing private key into keystore
cast wallet import deployer --interactive

Use in deployment:

# Deploy using named account
forge script script/Deploy.s.sol:DeployScript \
  --rpc-url $RPC_URL \
  --account deployer \
  --sender 0xYourAddress \
  --broadcast

Update your script to use the account:

contract DeployScript is Script {
    function run() external {
        // No private key needed - uses --account flag
        vm.startBroadcast();

        MyContract myContract = new MyContract();

        vm.stopBroadcast();

        console.log("MyContract deployed to:", address(myContract));
    }
}

3. Interactive Private Key (Development Only)

# Prompts for private key (not stored anywhere)
forge script script/Deploy.s.sol:DeployScript \
  --rpc-url $RPC_URL \
  --private-key-interactive \
  --broadcast

4. .env Variables (Development/Testing ONLY)

⚠️ Use ONLY for local development or testnet testing with non-production keys!

contract DeployScript is Script {
    function run() external {
        uint256 deployerPrivateKey = vm.envUint("PRIVATE_KEY");

        vm.startBroadcast(deployerPrivateKey);

        MyContract myContract = new MyContract();

        vm.stopBroadcast();

        console.log("MyContract deployed to:", address(myContract));
    }
}

If using .env:

• ✅ Only use accounts created specifically for development/testing
• ✅ Never reuse production private keys
• ✅ Keep test funds minimal
• ✅ Add .env to .gitignore
• ❌ Never commit .env to version control
• ❌ Never use for mainnet deployments

Deployment Setup

Deploy Commands

# Dry run (simulation)
forge script script/Deploy.s.sol:DeployScript --rpc-url $RPC_URL

# Actual deployment with hardware wallet (RECOMMENDED for production)
forge script script/Deploy.s.sol:DeployScript \
  --rpc-url $RPC_URL \
  --ledger \
  --broadcast \
  --verify

# Actual deployment with cast wallet (RECOMMENDED for all deployments)
forge script script/Deploy.s.sol:DeployScript \
  --rpc-url $RPC_URL \
  --account deployer \
  --sender 0xYourAddress \
  --broadcast \
  --verify

# Development only: with .env private key
forge script script/Deploy.s.sol:DeployScript \
  --rpc-url $RPC_URL \
  --broadcast \
  --verify

Best Practices

1. Secure private key management - Use hardware wallets or cast wallet for all deployments; never store production keys in .env
2. Use profiles - Create different profiles for dev, test, production
3. High optimizer runs for production - Use 10,000+ optimizer runs for deployed contracts
4. Comprehensive .env.example - Document all required environment variables (but discourage private keys)
5. Git submodules for deps - Let Foundry manage dependencies via git
6. Separate test directories - Use test/foundry/ for Foundry tests in hybrid setups
7. Enable via-ir for optimization - Use via_ir = true for complex contracts
8. Version pin Solidity - Specify exact solc_version in foundry.toml

Troubleshooting

Issue: "forge: command not found"

# Install/update Foundry
curl -L https://foundry.paradigm.xyz | bash
foundryup

Issue: Dependency conflicts in hybrid setup

# Prioritize Foundry libs over node_modules
libs = ["lib", "node_modules"]

Issue: Compilation errors with remappings

# Regenerate remappings
forge remappings > remappings.txt

Issue: Tests not found

# Check test file naming (must end in .t.sol)
mv test/MyTest.sol test/MyTest.t.sol

Quick Reference

| Task | Command | Notes | |------|---------|-------| | Init project | forge init | Creates new project | | Add dependency | forge install <repo> | Uses git submodules | | Build | forge build | Compiles contracts | | Test | forge test | Runs tests | | Coverage | forge coverage | Test coverage | | Gas report | forge test --gas-report | Gas usage | | Format | forge fmt | Code formatting | | Deploy | forge script | Run deployment | | Verify | forge verify-contract | Verify on Etherscan |

Template Files

This skill provides the following templates:

• ./templates/foundry.toml - Complete Foundry configuration
• ./templates/.env.example - Environment variables template

Scripts

This skill provides the following scripts:

• ./scripts/init-foundry.sh - Automated project initialization

---

Next Steps After Setup:

1. Configure foundry.toml for your specific needs
2. Copy .env.example to .env and fill in values
3. Install required dependencies with forge install
4. Write contracts in src/
5. Write tests in test/
6. Run forge test to verify setup