web3-testing

name web3-testing description 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. 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 // 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 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) // 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 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 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 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.