/foundry-solidity

name: foundry-solidity
description: Build and test Solidity contracts with Foundry. Use when developing Ethereum contracts, writing Forge tests, deploying with scripts, or debugging with Cast/Anvil. Triggers on forge, cast, anvil, foundry.toml, *.t.sol, or *.s.sol.
metadata:
  version: "0.2.5"
  categories: "development"
  topics: "solidity, foundry, forge, smart-contracts, ethereum"
  openclaw:
    homepage: https://github.com/tenequm/skills/tree/main/skills/foundry-solidity
    emoji: "⚒️"
    primaryEnv: PRIVATE_KEY
    requires:
      anyBins:
        - forge
        - cast
    install:
      - kind: brew
        formula: foundry
        bins:
          - forge
          - cast
          - anvil
    envVars:
      - name: PRIVATE_KEY
        required: false
        description: Deployer signing key. Use throwaway/testnet keys.
      - name: ETHERSCAN_API_KEY
        required: false
        description: Etherscan verification API key.
      - name: MAINNET_RPC_URL
        required: false
        description: Ethereum mainnet RPC endpoint.
      - name: SEPOLIA_RPC_URL
        required: false
        description: Sepolia testnet RPC endpoint.
      - name: ARBITRUM_RPC_URL
        required: false
        description: Arbitrum RPC endpoint.
      - name: OPTIMISM_RPC_URL
        required: false
        description: Optimism RPC endpoint.
      - name: ARBISCAN_API_KEY
        required: false
        description: Arbiscan verification key.
      - name: OPTIMISTIC_ETHERSCAN_API_KEY
        required: false
        description: Optimistic Etherscan verification key.
      - name: POLYGONSCAN_API_KEY
        required: false
        description: Polygonscan verification key.
      - name: BASESCAN_API_KEY
        required: false
        description: Basescan verification key.
      - name: DEPLOYER_PRIVATE_KEY
        required: false
        description: Alternative deployer key alias.
      - name: TEST_ADMIN
        required: false
        description: Test admin address used in fork tests.

Foundry Solidity Development

Complete guide for building secure, efficient smart contracts with **Foundry 1.5.0** and **Solidity 0.8.30**.

When to Use This Skill

• Developing Ethereum/EVM smart contracts
• Writing Forge tests (unit, fuzz, invariant, fork)
• Deploying contracts with scripts
• Using Foundry tools (forge, cast, anvil, chisel)
• Working with `foundry.toml`, `*.t.sol`, `*.s.sol` files
• Debugging transactions and contract interactions

Quick Start

# Create new project
forge init my-project && cd my-project

# Build contracts
forge build

# Run tests
forge test

# Deploy (dry-run)
forge script script/Deploy.s.sol --rpc-url sepolia

# Deploy (broadcast)
forge script script/Deploy.s.sol --rpc-url sepolia --broadcast --verify

Project Structure

my-project/
├── foundry.toml          # Configuration
├── src/                  # Contracts
│   └── Counter.sol
├── test/                 # Tests (*.t.sol)
│   └── Counter.t.sol
├── script/               # Deploy scripts (*.s.sol)
│   └── Deploy.s.sol
└── lib/                  # Dependencies
    └── forge-std/

Core Commands

Build & Test

forge build                          # Compile
forge test                           # Run all tests
forge test -vvvv                     # With traces
forge test --match-test testDeposit  # Filter by test name
forge test --match-contract Vault    # Filter by contract
forge test --fork-url $RPC_URL       # Fork testing
forge test --gas-report              # Gas usage report

Deployment

# Single contract
forge create src/Token.sol:Token --rpc-url sepolia --private-key $KEY --broadcast

# Script deployment (recommended)
forge script script/Deploy.s.sol:Deploy --rpc-url sepolia --broadcast --verify

# Verify existing contract
forge verify-contract $ADDRESS src/Token.sol:Token --chain sepolia

Cast - Blockchain Interactions

cast call $CONTRACT "balanceOf(address)" $USER --rpc-url mainnet
cast send $CONTRACT "transfer(address,uint256)" $TO $AMOUNT --private-key $KEY
cast decode-tx $TX_HASH
cast storage $CONTRACT 0 --rpc-url mainnet

Anvil - Local Node

anvil                           # Start local node
anvil --fork-url $RPC_URL       # Fork mainnet
anvil --fork-block-number 18000000

Basic Test Contract

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

import {Test, console} from "forge-std/Test.sol";
import {Counter} from "../src/Counter.sol";

contract CounterTest is Test {
    Counter public counter;
    address public user;

    function setUp() public {
        counter = new Counter();
        user = makeAddr("user");
        deal(user, 10 ether);
    }

    function test_Increment() public {
        counter.increment();
        assertEq(counter.number(), 1);
    }

    function test_RevertWhen_Unauthorized() public {
        vm.expectRevert("Unauthorized");
        vm.prank(user);
        counter.adminFunction();
    }

    function testFuzz_SetNumber(uint256 x) public {
        x = bound(x, 0, 1000);
        counter.setNumber(x);
        assertEq(counter.number(), x);
    }
}

Essential Cheatcodes

// Identity & ETH
address alice = makeAddr("alice");          // Create labeled address
deal(alice, 10 ether);                      // Give ETH
deal(address(token), alice, 1000e18);       // Give ERC20

// Impersonation
vm.prank(alice);                            // Next call as alice
vm.startPrank(alice);                       // All calls as alice
vm.stopPrank();

// Time & Block
vm.warp(block.timestamp + 1 days);          // Set timestamp
vm.roll(block.number + 100);                // Set block number

// Assertions
vm.expectRevert("Error message");           // Expect revert
vm.expectRevert(CustomError.selector);      // Custom error
vm.expectEmit(true, true, false, true);     // Expect event
emit Transfer(from, to, amount);            // Must match next emit

// Sto