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
{ uint256 temp = x + y; }

// 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