Hardhat: impersonate signer when forking

01_impersonateSigner.js

const SwapRouterArtifact = require('@uniswap/v3-periphery/artifacts/contracts/SwapRouter.sol/SwapRouter.json')

const erc20Abi = [
    {
        "inputs": [
            {"internalType": "address", "name": "spender", "type": "address"},
            {"internalType": "uint256", "name": "amount", "type": "uint256"}
        ],
        "name": "approve",
        "outputs": [{"internalType": "bool", "name": "", "type": "bool"}],
        "stateMutability": "nonpayable", "type": "function"
    },
    {
        "inputs": [{"internalType": "address", "name": "account", "type": "address"}],
        "name": "balanceOf",
        "outputs": [{"internalType": "uint256", "name": "", "type": "uint256"}],
        "stateMutability": "view",
        "type": "function"
    }
]

const hardhat = require("hardhat")
const provider = hardhat.ethers.provider
const RECIPIENT = '0xAb5801a7D398351b8bE11C439e05C5B3259aeC9B'


const wethAddress = '0xc02aaa39b223fe8d0a0e5c4f27ead9083c756cc2'
const usdcAddress = '0xa0b86991c6218b36c1d19d4a2e9eb0ce3606eb48'
const routerAddress = '0xE592427A0AEce92De3Edee1F18E0157C05861564'
const weth = new hardhat.ethers.Contract(wethAddress, erc20Abi, provider)
const usdc = new hardhat.ethers.Contract(usdcAddress, erc20Abi, provider)
const router =  new hardhat.ethers.Contract(routerAddress, SwapRouterArtifact.abi, provider)


const logBalances = async () => {
    const wethBalance = await weth.balanceOf(RECIPIENT)
    const usdcBalance = await usdc.balanceOf(RECIPIENT)
    console.log('wethBalance', hardhat.ethers.utils.formatUnits(wethBalance, 18))
    console.log('usdcBalance', hardhat.ethers.utils.formatUnits(usdcBalance, 6))
}


const main = async () => {
    const signer = await hardhat.ethers.getImpersonatedSigner(RECIPIENT);

    console.log('------------ Time 0')
    await logBalances()

    const tokensIn = '10'
    const amountIn = hardhat.ethers.utils.parseUnits(tokensIn, 18)
    const gasLimit = 1_000_000

    await weth.connect(signer).approve(router.address, amountIn)

    const params = {
        tokenIn: weth.address,
        tokenOut: usdc.address,
        recipient: RECIPIENT,
        deadline: Math.floor(Date.now() / 1000 + (10 * 60)),
        amountIn,
        fee: 500,
        amountOutMinimum: 0,
        sqrtPriceLimitX96: 0,
    }

    const txInput = await router.connect(signer).exactInputSingle(params, { gasLimit })
    await txInput.wait()

    console.log('------------ Time 1')
    await logBalances()
}

/*
    node scripts/01_impersonateSigner.js
*/

main()
    .then(() => process.exit(0))
    .catch((error) => {
        console.error(error);
        process.exit(1);
    });

hardhat.config.js

require("@nomiclabs/hardhat-waffle");

/** @type import('hardhat/config').HardhatUserConfig */
module.exports = {
  solidity: "0.8.18",
  networks: {
    hardhat: {
      forking: {
        url: <YOUR_INFURA_URL>
      }
    }
  }
};

package.json

{
  "name": "YouTubeTutorials",
  "version": "1.0.0",
  "description": "",
  "main": "index.js",
  "scripts": {
    "test": "echo \"Error: no test specified\" && exit 1"
  },
  "keywords": [],
  "author": "",
  "license": "ISC",
  "dependencies": {
    "@nomiclabs/hardhat-ethers": "^2.2.3",
    "@nomiclabs/hardhat-waffle": "^2.0.6",
    "@types/sinon-chai": "^3.2.9",
    "@uniswap/sdk": "^3.0.3",
    "@uniswap/sdk-core": "^4.0.2",
    "@uniswap/v3-core": "^1.0.1",
    "@uniswap/v3-periphery": "^1.4.3",
    "@uniswap/v3-sdk": "^3.9.0",
    "ethereum-waffle": "^4.0.10",
    "ethers": "^5.7.2",
    "hardhat": "^2.14.0"
  }
}