Solidity Development Skill

Master Solidity smart contract development with design patterns, testing strategies, and production best practices.

Quick Start

Invoke this skill for Solidity development

Skill("solidity-development", topic="patterns", solidity_version="0.8.24")

Topics Covered 1. Language Features (0.8.x)

Modern Solidity essentials:

Data Types: Value, reference, mappings Functions: Visibility, modifiers, overloading Inheritance: Diamond problem, C3 linearization Custom Errors: Gas-efficient error handling 2. Design Patterns

Battle-tested patterns:

CEI: Checks-Effects-Interactions Factory: Contract deployment patterns Proxy: Upgradeable contracts Access Control: RBAC, Ownable 3. Testing

Comprehensive test strategies:

Unit Tests: Foundry, Hardhat Fuzz Testing: Property-based testing Invariant Testing: System-wide properties Fork Testing: Mainnet simulation 4. Upgradability

Safe upgrade patterns:

UUPS: Self-upgrading proxy Transparent: Admin separation Beacon: Shared implementation Diamond: Multi-facet Code Examples CEI Pattern // SPDX-License-Identifier: MIT pragma solidity ^0.8.24;

contract SecureVault { mapping(address => uint256) public balances;

error InsufficientBalance();
error TransferFailed();

function withdraw(uint256 amount) external {
    // 1. CHECKS
    if (balances[msg.sender] < amount) revert InsufficientBalance();

    // 2. EFFECTS
    balances[msg.sender] -= amount;

    // 3. INTERACTIONS
    (bool ok,) = msg.sender.call{value: amount}("");
    if (!ok) revert TransferFailed();
}

}

Factory Pattern contract TokenFactory { event TokenCreated(address indexed token, address indexed owner);

function createToken(
    string memory name,
    string memory symbol
) external returns (address) {
    Token token = new Token(name, symbol, msg.sender);
    emit TokenCreated(address(token), msg.sender);
    return address(token);
}

}

Foundry Test // SPDX-License-Identifier: MIT pragma solidity ^0.8.24;

import "forge-std/Test.sol";

contract VaultTest is Test { Vault vault; address alice = makeAddr("alice");

function setUp() public {
    vault = new Vault();
    vm.deal(alice, 10 ether);
}

function test_Deposit() public {
    vm.prank(alice);
    vault.deposit{value: 1 ether}();

    assertEq(vault.balances(alice), 1 ether);
}

function testFuzz_Withdraw(uint256 amount) public {
    amount = bound(amount, 0.01 ether, 10 ether);

    vm.startPrank(alice);
    vault.deposit{value: amount}();
    vault.withdraw(amount);
    vm.stopPrank();

    assertEq(vault.balances(alice), 0);
}

function test_RevertWhen_InsufficientBalance() public {
    vm.prank(alice);
    vm.expectRevert(Vault.InsufficientBalance.selector);
    vault.withdraw(1 ether);
}

}

Pattern Reference Pattern Use Case Complexity CEI All state changes Low Factory Multiple instances Low Clone (1167) Gas-efficient copies Medium UUPS Upgradeable Medium Diamond Unlimited size High Common Pitfalls Pitfall Issue Solution Stack too deep >16 variables Use structs or helpers Contract too large >24KB Split into libraries Reentrancy State after call Use CEI pattern Missing access Anyone can call Add modifiers Troubleshooting "Stack too deep" // Solution 1: Use struct struct Params { uint256 a; uint256 b; uint256 c; }

// Solution 2: Block scoping

// Solution 3: Internal function function _helper(uint256 a) internal { }

"Contract size exceeds limit"

Check contract sizes

forge build --sizes

Solutions: Split into libraries, use Diamond pattern.

Security Checklist CEI pattern on all withdrawals Access control on admin functions Input validation (zero address, bounds) Reentrancy guards on external calls Event emission for state changes Custom errors for gas efficiency CLI Commands

Development workflow

forge init # New project forge build # Compile forge test -vvv # Run tests forge coverage # Coverage report forge fmt # Format code forge snapshot # Gas snapshot

Cross-References Bonded Agent: 03-solidity-expert Related Skills: ethereum-development, smart-contract-security Version History Version Date Changes 2.0.0 2025-01 Production-grade with Foundry, patterns 1.0.0 2024-12 Initial release