web3-testing

# 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.