Yes, you can deploy smart contracts using Hardhat on Ethereum testnets like Rinkeby or Kovan. This process allows you to test your smart contracts in a live environment without using real Ether. In this guide, we will walk you through the steps required to deploy your contracts on these testnets.

Prerequisites

• Basic knowledge of JavaScript and Solidity.
• A Hardhat project set up with smart contracts.
• Node.js installed on your machine.
• An Ethereum wallet (like MetaMask) with test Ether for deployment.
• An Infura or Alchemy account (or any Ethereum node provider) to connect to the testnets.

Setting Up Your Hardhat Project

If you haven't set up a Hardhat project yet, follow these steps:

mkdir my-hardhat-project
cd my-hardhat-project
npm init --yes
npm install --save-dev hardhat
npx hardhat

Create a simple smart contract in the contracts directory, such as Greeter.sol:

pragma solidity ^0.8.0;

contract Greeter {
    string public greeting;

    constructor(string memory _greeting) {
        greeting = _greeting;
    }

    function greet() public view returns (string memory) {
        return greeting;
    }

    function setGreeting(string memory _greeting) public {
        greeting = _greeting;
    }
}

Installing Required Dependencies

To deploy to testnets, you will need the @nomiclabs/hardhat-ethers and @nomiclabs/hardhat-waffle plugins:

npm install --save-dev @nomiclabs/hardhat-ethers @nomiclabs/hardhat-waffle ethers

Configuring Hardhat for Testnets

You need to configure Hardhat to connect to the testnets. Open the hardhat.config.js file and add the following configuration:

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

const { task } = require("hardhat/config");

// Replace with your Infura or Alchemy project ID and wallet private key
const INFURA_PROJECT_ID = "your_infura_project_id"; // Replace with your Infura project ID
const PRIVATE_KEY = "your_wallet_private_key"; // Replace with your wallet private key

module.exports = {
    solidity: "0.8.0",
    networks: {
        rinkeby: {
            url: `https://rinkeby.infura.io/v3/${INFURA_PROJECT_ID}`,
            accounts: [`0x${PRIVATE_KEY}`]
        },
        kovan: {
            url: `https://kovan.infura.io/v3/${INFURA_PROJECT_ID}`,
            accounts: [`0x${PRIVATE_KEY}`]
        }
    }
};

Make sure to replace your_infura_project_id and contracts0 with your actual Infura project ID and your wallet's private key. You can obtain test Ether from a faucet for the respective testnets.

Creating a Deployment Script

Create a new deployment script in the contracts1 directory named contracts2:

contracts3

Deploying to the Testnet

Now you are ready to deploy your contract to the Rinkeby testnet. Run the following command in your terminal:

contracts4

For deploying to Kovan, you can run:

contracts5

Upon successful deployment, you will see the contract address printed in the console.

Verifying the Deployment

After deploying your contract, you may want to verify it on Etherscan for the respective testnet. To do this, you can use the contracts6 plugin. First, install the plugin:

contracts7

Then, add the Etherscan API key to your hardhat.config.js:

contracts9

To verify your contract, run the following command:

Greeter.sol0

Replace Greeter.sol1 with the actual address of your deployed contract. For Kovan, simply change the network parameter:

Greeter.sol2

Conclusion

Deploying smart contracts on Ethereum testnets like Rinkeby or Kovan using Hardhat is a straightforward process. By following the steps outlined in this guide, you can test your contracts in a live environment without the risk of losing real Ether. This allows for thorough testing and debugging before deploying to the Ethereum mainnet.