Metamask: Test Metamask interactions from a hardhat project?

Testing Interactions Between Your Contract and Metamask in a Hardhat Project

In the Ethereum ecosystem, interacting with external wallets such as MetaMask requires careful attention to security, usability, and testing. One way to test interactions between your smart contracts and MetaMask is to use a combination of tools from a hardhat project. In this article, we will explore how to achieve this.

Problem:

When you want to interact with an external wallet such as Metamask in your contract, you need to:

• Send the private key or user token to your contract.

• Use the web3 library to send the transaction.

• Verify the response from MetaMask.

This process requires several steps and is prone to errors if not done correctly. To simplify this process, we will use a hardhat project as a bridge between our contract’s interaction with MetaMask and the browser environment.

Setting up the hat

First, install Hardhat by running npx hardhat --run in watch (or npx hardhat -w). This command installs the dependencies needed to test the interactions between your contract and Metamask. You can also use yarn add hardhat to get started.

Creating a new contract

Create a new Solidity smart contract using Webpack, Ethers.js, or Truffle. For this example, we will use Truffle.

// src/contracts/MyContract.sol
solidity pragma ^0.8.0;
contract MyContract {
map(address => uint256) public balances;
function deposit(uint256 amount) public paid {
balances[msg.sender] += amount;
}
function draw(uint256 amount) public {
require(balances[msg.sender] >= amount, "Insufficient balance");
balances[msg.sender] -= sum;
}
}

Writing a hard hat test

Create a new file called mycontract.test.js in the root of your project:

const { await } = require("chai");
asynchronous function testMetamask() {
const myContract = await web3.eth.getContractAt("0x..."); // replace with your contract address
// Send the user's private key to the contract
myContract.sendTransaction({
from: "0x...",
to: "0x...",
value: 1 ether, // replace with your user's private key
});
const soldsBefore = await web3.eth.getBalance("0x..."); // replace with your user's address
await(balancesBefore).to.equal(0);
// Use Web3 to send the transaction to Metamask
myContract.sendTransaction({
from: "0x...",
to: "0x...",
value: web3.utils.toWei ("1", "ether"), // replace with the user's private key and token type (e.g. wei for ether)
data: "Hello, MetaMask!",
});
}

Executing the test

To run the test in a development environment:

npx hardhat run mycontract.test.js

• Replace the placeholder values ​​(e.g. contract address, user private key value) in the filemycontract.test.js''.

• Update thebalancesBeforevariable to reflect our user's new balance after interacting with MetaMask.

“javascript

// Update the balances before the transaction

const soldsBefore = await web3.eth.getBalance(“0x…”); // replace with your user’s address

await(balancesBefore).a.equal(1);

// Use Web3 to send the transaction to Metamask

myContract.sendTransaction({

from: “0x…”,

to: “0x…”,

value: web3.utils.toWei(“2”, “ether”), // replace with the user’s private key and token type (e.g. wei for ether)

data: “Hello, MetaMask!