Web3 Testing

When to use this skill

Use Web3 Testing when an AI agent needs a reusable SKILL.md workflow for this job: Test smart contracts comprehensively using Hardhat and Foundry with unit tests, integration tests, and mainnet forking. Use when testing Solidity contracts, setting up blockchain test suites, or validating DeFi protocols.

When not to use it

Skip Web3 Testing when the task is outside the coding category, or when a more specific skill in this directory already covers the same workflow with clearer triggers.

How to install

1. Personal install: create ~/.claude/skills/web3-testing/SKILL.md (and any bundled scripts) so Claude Code, Claude Desktop, and compatible agents can load it in every project.
2. Project install: commit the same folder at .claude/skills/web3-testing/ so teammates get the skill with the repo.
3. Restart the agent session after copying files so it re-scans the skills directory, then ask for the task in words that match the skill description.

Full install guide for Claude, Cursor, and Codex

What this skill does

# Web3 Smart Contract Testing

Master comprehensive testing strategies for smart contracts using Hardhat, Foundry, and advanced testing patterns.

## When to Use This Skill

- Writing unit tests for smart contracts - Setting up integration test suites - Performing gas optimization testing - Fuzzing for edge cases - Forking mainnet for realistic testing - Automating test coverage reporting - Verifying contracts on Etherscan

## Hardhat Testing Setup

```javascript // hardhat.config.js require("@nomicfoundation/hardhat-toolbox"); require("@nomiclabs/hardhat-etherscan"); require("hardhat-gas-reporter"); require("solidity-coverage");

module.exports = { solidity: { version: "0.8.19", settings: { optimizer: { enabled: true, runs: 200, }, }, }, networks: { hardhat: { forking: { url: process.env.MAINNET_RPC_URL, blockNumber: 15000000, }, }, goerli: { url: process.env.GOERLI_RPC_URL, accounts: [process.env.PRIVATE_KEY], }, }, gasReporter: { enabled: true, currency: "USD", coinmarketcap: process.env.COINMARKETCAP_API_KEY, }, etherscan: { apiKey: process.env.ETHERSCAN_API_KEY, }, }; ```

## Unit Testing Patterns

```javascript const { expect } = require("chai"); const { ethers } = require("hardhat"); const { loadFixture, time, } = require("@nomicfoundation/hardhat-network-helpers");

describe("Token Contract", function () { // Fixture for test setup async function deployTokenFixture() { const [owner, addr1, addr2] = await ethers.getSigners();

const Token = await ethers.getContractFactory("Token"); const token = await Token.deploy();

return { token, owner, addr1, addr2 }; }

describe("Deployment", function () { it("Should set the right owner", async function () { const { token, owner } = await loadFixture(deployTokenFixture); expect(await token.owner()).to.equal(owner.address); });

it("Should assign total supply to owner", async function () { const { token, owner } = await loadFixture(deployTokenFixture); const ownerBalance = await token.balanceOf(owner.address); expect(await token.totalSupply()).to.equal(ownerBalance); }); });

describe("Transactions", function () { it("Should transfer tokens between accounts", async function () { const { token, owner, addr1 } = await loadFixture(deployTokenFixture);

await expect(token.transfer(addr1.address, 50)).to.changeTokenBalances( token, [owner, addr1], [-50, 50], ); });

it("Should fail if sender doesn't have enough tokens", async function () { const { token, addr1 } = await loadFixture(deployTokenFixture); const initialBalance = await token.balanceOf(addr1.address);

await expect( token.connect(addr1).transfer(owner.address, 1), ).to.be.revertedWith("Insufficient balance"); });

it("Should emit Transfer event", async function () { const { token, owner, addr1 } = await loadFixture(deployTokenFixture);

await expect(token.transfer(addr1.address, 50)) .to.emit(token, "Transfer") .withArgs(owner.address, addr1.address, 50); }); });

describe("Time-based tests", function () { it("Should handle time-locked operations", async function () { const { token } = await loadFixture(deployTokenFixture);

// Increase time by 1 day await time.increase(86400);

// Test time-dependent functionality }); });

describe("Gas optimization", function () { it("Should use gas efficiently", async function () { const { token } = await loadFixture(deployTokenFixture);

const tx = await token.transfer(addr1.address, 100); const receipt = await tx.wait();

expect(receipt.gasUsed).to.be.lessThan(50000); }); }); }); ```

## Foundry Testing (Forge)

```solidity // SPDX-License-Identifier: MIT pragma solidity ^0.8.0;

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

contract TokenTest is Test { Token token; address owner = address(1); address user1 = address(2); address user2 = address(3);

function setUp() public { vm.prank(owner); token = new Token(); }

function testInitialSupply() public { assertEq(token.totalSupply(), 1000000 * 10**18); }

function testTransfer() public { vm.prank(owner); token.transfer(user1, 100);

assertEq(token.balanceOf(user1), 100); assertEq(token.balanceOf(owner), token.totalSupply() - 100); }

function testFailTransferInsufficientBalance() public { vm.prank(user1); token.transfer(user2, 100); // Should fail }

function testCannotTransferToZeroAddress() public { vm.prank(owner); vm.expectRevert("Invalid recipient"); token.transfer(address(0), 100); }

// Fuzzing test function testFuzzTransfer(uint256 amount) public { vm.assume(amount > 0 && amount <= token.totalSupply());

vm.prank(owner); token.transfer(user1, amount);

assertEq(token.balanceOf(user1), amount); }

// Test with cheatcodes function testDealAndPrank() public { // Give ETH to address vm.deal(user1, 10 ether);

// Impersonate address vm.prank(user1);

// Test functionality assertEq(user1.balance, 10 ether); }

// Mainnet fork test function testForkMainnet() public { vm.createSelectFork("https://eth-mainnet.alchemyapi.io/v2/...");

// Interact with mainnet contracts address dai = 0x6B175474E89094C44Da98b954EedeAC495271d0F; assertEq(IERC20(dai).symbol(), "DAI"); } } ```

## Advanced Testing Patterns

### Snapshot and Revert

```javascript describe("Complex State Changes", function () { let snapshotId;

beforeEach(async function () { snapshotId = await network.provider.send("evm_snapshot"); });

afterEach(async function () { await network.provider.send("evm_revert", [snapshotId]); });

it("Test 1", async function () { // Make state changes });

it("Test 2", async function () { // State reverted, clean slate }); }); ```

### Mainnet Forking

```javascript describe("Mainnet Fork Tests", function () { let uniswapRouter, dai, usdc;

before(async function () { await network.provider.request({ method: "hardhat_reset", params: [ { forking: { jsonRpcUrl: process.env.MAINNET_RPC_URL, blockNumber: 15000000, }, }, ], });

// Connect to existing mainnet contracts uniswapRouter = await ethers.getContractAt( "IUniswapV2Router", "0x7a250d5630B4cF539739dF2C5dAcb4c659F2488D", );

dai = await ethers.getContractAt( "IERC20", "0x6B175474E89094C44Da98b954EedeAC495271d0F", ); });

it("Should swap on Uniswap", async function () { // Test with real Uniswap contracts }); }); ```

### Impersonating Accounts

```javascript it("Should impersonate whale account", async function () { const whaleAddress = "0x...";

await network.provider.request({ method: "hardhat_impersonateAccount", params: [whaleAddress], });

const whale = await ethers.getSigner(whaleAddress);

// Use whale's tokens await dai .connect(whale) .transfer(addr1.address, ethers.utils.parseEther("1000")); }); ```

## Additional patterns and templates

More detailed templates and worked examples live in `references/details.md`. Read that file for the full pattern library.

Intended uses

• Writing unit tests for smart contracts
• Setting up integration test suites
• Performing gas optimization testing
• Fuzzing for edge cases
• Forking mainnet for realistic testing
• Automating test coverage reporting
• Verifying contracts on Etherscan