Hardhat Toolchain Reference

Core Commands

npx hardhat compile            # Compile contracts
npx hardhat test               # Run tests
npx hardhat test --grep "mint" # Filter tests
npx hardhat node               # Local node
npx hardhat run scripts/deploy.ts --network sepolia  # Deploy
npx hardhat verify --network mainnet ADDR arg1 arg2  # Verify
npx hardhat coverage           # Test coverage
npx hardhat clean              # Clean artifacts

Configuration

hardhat.config.ts

import { HardhatUserConfig } from "hardhat/config"
import "@nomicfoundation/hardhat-toolbox" // ethers, chai, coverage, gas, typechain, verify
import "hardhat-deploy" // optional: deployment management

const config: HardhatUserConfig = {
  solidity: {
    version: "0.8.28",
    settings: {
      optimizer: { enabled: true, runs: 200 },
      viaIR: false,
    },
  },
  networks: {
    hardhat: {
      forking: {
        url: process.env.ETH_RPC_URL || "",
        enabled: !!process.env.FORK,
      },
    },
    mainnet: {
      url: process.env.ETH_RPC_URL || "",
      accounts: process.env.DEPLOYER_KEY ? [process.env.DEPLOYER_KEY] : [],
    },
    base: {
      url: process.env.BASE_RPC_URL || "https://mainnet.base.org",
      accounts: process.env.DEPLOYER_KEY ? [process.env.DEPLOYER_KEY] : [],
    },
    sepolia: {
      url: process.env.SEPOLIA_RPC_URL || "",
      accounts: process.env.DEPLOYER_KEY ? [process.env.DEPLOYER_KEY] : [],
    },
  },
  etherscan: {
    apiKey: {
      mainnet: process.env.ETHERSCAN_API_KEY || "",
      base: process.env.BASESCAN_API_KEY || "",
    },
  },
}

export default config

Testing (ethers.js + chai)

Basic Test

import { expect } from "chai"
import { ethers } from "hardhat"
import { loadFixture } from "@nomicfoundation/hardhat-toolbox/network-helpers"

describe("MyToken", function () {
  async function deployFixture() {
    const [owner, alice, bob] = await ethers.getSigners()
    const Token = await ethers.getContractFactory("MyToken")
    const token = await Token.deploy("MyToken", "MTK")
    return { token, owner, alice, bob }
  }

  it("should mint tokens", async function () {
    const { token, alice } = await loadFixture(deployFixture)
    await token.connect(alice).mint(100)
    expect(await token.balanceOf(alice.address)).to.equal(100)
  })
})

Fixtures (loadFixture)

• Snapshot and revert between tests — much faster than redeploying
• Always use loadFixture over beforeEach for deployment

Time Manipulation

import { time } from "@nomicfoundation/hardhat-toolbox/network-helpers"

await time.increase(3600)          // Advance 1 hour
await time.increaseTo(timestamp)   // Set to specific time
await time.latest()                // Get current block timestamp

Event Testing

await expect(token.transfer(alice.address, 100))
  .to.emit(token, "Transfer")
  .withArgs(owner.address, alice.address, 100)

Revert Testing

await expect(token.connect(alice).adminMint(100))
  .to.be.revertedWithCustomError(token, "OwnableUnauthorizedAccount")
  .withArgs(alice.address)

Deployment

Using Hardhat Ignition (recommended)

// ignition/modules/MyToken.ts
import { buildModule } from "@nomicfoundation/hardhat-ignition/modules"

export default buildModule("MyToken", (m) => {
  const token = m.contract("MyToken", ["MyToken", "MTK"])
  return { token }
})

npx hardhat ignition deploy ignition/modules/MyToken.ts --network sepolia

Using Scripts

// scripts/deploy.ts
import { ethers } from "hardhat"

async function main() {
  const Token = await ethers.getContractFactory("MyToken")
  const token = await Token.deploy("MyToken", "MTK")
  await token.waitForDeployment()
  console.log("Deployed to:", await token.getAddress())
}

main().catch(console.error)

Common Plugins

Plugin	Purpose
@nomicfoundation/hardhat-toolbox	All-in-one (ethers, chai, coverage, etc.)
@nomicfoundation/hardhat-verify	Contract verification
hardhat-deploy	Deployment management
hardhat-gas-reporter	Gas usage per function
@typechain/hardhat	TypeScript types for contracts
solidity-coverage	Test coverage

Hardhat vs Foundry

Feature	Hardhat	Foundry
Language	TypeScript	Solidity
Speed	Slower	Much faster
Ecosystem	Larger plugin ecosystem	Growing
Testing	JS/TS tests	Solidity tests
Fuzzing	Limited	Built-in
Debugging	console.log	Traces + console.log
Best for	JS/TS teams, complex deploy	Performance, Solidity-native

Many projects use both: Foundry for testing, Hardhat for deployment/scripts.

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