Mainnet Forking Config

Setting up the environment

Linux

sudo apt update

sudo apt install curl git

curl -sL https://deb.nodesource.com/setup_12.x | sudo -E bash -

sudo apt install nodejs

MacOS

curl -o- https://raw.githubusercontent.com/creationix/nvm/v0.35.2/install.sh | bash

nvm install 12

nvm use 12

nvm alias default 12

npm install npm --global # Upgrade npm to the latest version

Windows

Download and run these:

1. Git's installer for Windows(opens new window)
2. node-v12.XX.XX-x64.msi from here(opens new window)#

Creating a new Hardhat project

Open a new terminal and run these commands:

mkdir hardhat-tutorial

cd hardhat-tutorial

npm init --yes

npm install --save-dev hardhat

In the same directory where you installed Hardhat run:

npx hardhat

Choose “Create an empty hardhat.config.js”

Plugins

For this tutorial we are going to use the Ethers.js and Waffle plugins. They'll allow you to interact with Ethereum and to test your contracts. We'll explain how they're used later on. To install them, in your project directory run: npm install --save-dev @nomiclabs/hardhat-ethers ethers @nomiclabs/hardhat-waffle ethereum-waffle chai

hardhat.config.js will look like

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

/**
 * @type import('hardhat/config').HardhatUserConfig
 */
module.exports = {
  solidity: "0.7.3",
};

Mainnet forking

To use this feature you need to connect to an archive node. We recommend using Alchemy

The easiest way to try this feature is to start a node from the command line:

npx hardhat node --fork https://eth-mainnet.alchemyapi.io/v2/<key>

You can also configure Hardhat Network to always do this:

networks: {
  hardhat: {
    forking: {
      url: "https://eth-mainnet.alchemyapi.io/v2/<key>",
	blockNumber: <blockNumber>,
    }
  }
}

(Note that you'll need to replace the  component of the URL with your personal Alchemy API key.)

Note: it’s recommended to include the blockNumber, which helps to accelerate the speed of the tests. However, putting a wrong blockNumber will result a wrong value, therefore, you might need to look for the exact blockNumber when doing the impersonation.

More about the mainnet forking with harhat (https://hardhat.org/hardhat-network/guides/mainnet-forking.html)

Interact with a live contract

1. Import the contract ABI

const BUSDABI = require("./BUSD-ABI.json");

NB: You would need to find the exact ABI of the contract and save it in the .json format, then import it into the test file as the above-mentioned code.

2. Initialize the contract’s address

const busdContract = "0xA8D394fE7380b8cE6145d5f85E6aC22d4E91ACDe"

NB: This is the live address of the contract

3. Impersonate the owner of the contract

await hre.network.provider.request({ method: "hardhat_impersonateAccount", params: ["0x6d26AA4356cEF4A641b387218fE1eF7887e3C630"], });

whiteBUSD = await ethers.getSigner("0x6d26AA4356cEF4A641b387218fE1eF7887e3C630");

4. Impersonate a live contract

BUSD = new ethers.Contract(busdContract, BUSDABI, whiteBUSD)

The BUSD is now becoming the contract variable, you can get all the characteristics of the contract such as: BUSD.address, BUSD.owner(), etc