Metamask: Test Metamask interactions from a hardhat project?

Testing Interactions Between Your Contract and MetaMask in the Hardhat Project

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

Problem:

When you want to interact with an external wallet like MetaMask in your contract, you need to:

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

• Use the web3 library to send the transaction.

• Verify the response from MetaMask.

This process requires multiple steps and is prone to errors if not performed correctly. To simplify this process, we will use the 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 necessary dependencies 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. We’ll use Truffle for this example.

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

Writing and hardhat test

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

const {escape} = 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 the amount of the user's private key
});
const balancesBefore = await web3.eth.getBalance("0x..."); // replace with your user's address
await(balanceBefore).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 user's private key amount and token type (eg wei for ether)

    data: "Hello, MetaMask!",

  });

}

Running the test

To run a test in a development environment:

npx hardhat run mycontract.test.js

In this example, we use Web3 to send transactions from the MyContract instance of our contract to the user’s Ethereum wallet. We then verify that the transaction was successful by checking our user’s balance.

Testing Interactions with MetaMask

To test the interaction between your contract and MetaMask:

• Replace the placeholder values ​​​​(e.g. contract address, user private key amount) in the mycontract.test.js file.

• Update the balancesBefore variable to reflect the new state of our user after interacting with MetaMask.

“`javascript

// Update the balance before the transaction

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

wait(balanceBefore).to.equal(1);

// Use Web3 to send the transaction to Metamask

myContract.sendTransaction({

from: “0x…”,

to: “0x…”,

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

data: “Hello, MetaMask!