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Jarret Moses
Jarret Moses

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How to Create a Custom "faucet" Task With Hardhat

Intro

When working locally to build your web3 project, you'll get to a point where you want to test the interactions with your smart contract. When you get to this point, you will need a wallet address with some ETH to pay for your gas fees. If you are using Hardhat as your development environment there is no out of the box command to achieve this. Luckily, Hardhat provides a mechanism for creating custom tasks which we can leverage to create a faucet to send ETH to our wallet for testing. To learn more about Hardhat tasks, you can read about them here.

Solution

The following code snippet is inspired by this boilerplate project and when done, you should have access to a new task called faucet.

// faucet.ts or faucet.js
import { task } from 'hardhat/config';

task('faucet', 'Sends ETH to an address')
  .addPositionalParam('receiver', 'The address that will receive them')
  .setAction(async ({ receiver }, hre) => {
    if (hre.network.name === 'hardhat') {
      console.warn(
        `You are running the faucet task with Hardhat network, which gets automatically created
        and destroyed every time. Use the Hardhat option '--network localhost'`,
      );
    }

    const [sender] = await hre.ethers.getSigners();
    const tx = await sender.sendTransaction({
      to: receiver,
      value: hre.ethers.constants.WeiPerEther.mul(5),
    });

    await tx.wait();

    console.log(`Transferred 5 ETH ${receiver}`);
  });
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then in your hardhat.config.ts (or hardhat.config.js) you just need to import the task

// hardhat.config.ts
import * as dotenv from 'dotenv';

import { HardhatUserConfig, task } from 'hardhat/config';
import '@nomiclabs/hardhat-etherscan';
import '@nomiclabs/hardhat-waffle';
import '@typechain/hardhat';
import 'hardhat-gas-reporter';
import 'solidity-coverage';
import '@nomiclabs/hardhat-ethers';

// Tasks
import './tasks/faucet.ts'; // <--IMPORTED FAUCET TASK

dotenv.config();

// This is a sample Hardhat task. To learn how to create your own go to
// https://hardhat.org/guides/create-task.html
task('accounts', 'Prints the list of accounts', async (taskArgs, hre) => {
  const accounts = await hre.ethers.getSigners();

  for (const account of accounts) {
    console.log(account.address);
  }
});
// You need to export an object to set up your config
// Go to https://hardhat.org/config/ to learn more

const config: HardhatUserConfig = {
  solidity: {
    version: '0.8.4',
  },
  networks: {
    hardhat: {
      chainId: 1337,
    },
    ropsten: {
      url: process.env.ROPSTEN_URL || '',
      accounts:
        process.env.PRIVATE_KEY !== undefined ? [process.env.PRIVATE_KEY] : [],
    },
  },
  gasReporter: {
    enabled: process.env.REPORT_GAS !== undefined,
    currency: 'USD',
  },
  etherscan: {
    apiKey: process.env.ETHERSCAN_API_KEY,
  },
};

export default config;
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(note your config file may look a little different)

Running this task requires you to have your local hardhat node running via npx hardhat node. When the node spins up you will see a bunch of addresses generated with ETH associated with them. This task gets reference to one of these addresses via await hre.ethers.getSigners() and sends ETH to the receiver param passed into the .setAction callback. The value is just set to wei and is using built in utilities to (in this case) send the equivalent of 5 ETH to the receiver via the sendTransaction call.

Now once you have done all this if you type npx hardhat in your hardhat project in your terminal, you should see faucet in your task list.Image description

If everything has worked and you see your new task, all you need to do now to use it is call the following command in your terminal npx hardhat --network localhost faucet WALLET_ADDRESS_HERE

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