E2E testing for dApps using Puppeteer + MetaMask

$ npm install -s dappeteer

import puppeteer from 'puppeteer'
import dappeteer from 'dappeteer'

async function main() {
  const browser = await dappeteer.launch(puppeteer)
  const metamask = await dappeteer.getMetamask(browser)
  
  // create or import an account
  // await metamask.createAccount()
  await metamask.importAccount('already turtle birth enroll since...')
  
  // you can change the network if you want
  await metamask.switchNetwork('ropsten')
  
  // go to a dapp and do something that prompts MetaMask to confirm a transaction
  const page = await browser.newPage()
  await page.goto('http://my-dapp.com')
  const payButton = await page.$('#pay-with-eth')
  await payButton.click()
  
  // 🏌
  await metamask.confirmTransaction()
}

main()

• dappeteer.launch(puppeteer[, launchOptions]): returns an instance of browser, same as puppeteer.launch, but it also installs the MetaMask extension. It supports all the regular puppeteer.launch options as a second argument with the addition of two extra ones:

  • metamaskPath: Path to the MetaMask extension (by default it uses the one bundled)

  • extensionUrl: URL of the MetaMask extension, by default it is chrome-extension://nkbihfbeogaeaoehlefnkodbefgpgknn/popup.html but if you use a different version you might need to change it use the right extension id.

• dappeteer.getMetaMask(browser): returns a promise that resolves to an object that allows you to interact with MetaMask by using the following methods:

  • metamask.createAccount([password]): it commands MetaMask to create a new account, it resolves when it's done. It can only be used while you haven't signed in yet, otherwise it throws. The password is optional, it defaults to password1234.

  • metamask.importAccount(seed[, password]): it commands MetaMask to import an account, you need to provide the twelve words seed. It can only be used while you haven't signed in yet, otherwise it throws. The password is optional, it defaults to password1234.

  • metamask.lock(): signs out from MetaMask. It can only be used if you arelady signed it, otherwise it throws.

  • metamask.unlock([password]): it unlocks the MetaMask extension. It can only be used in you locked/signed out before, otherwise it throws. The password is optional, it defaults to password1234.

  • metamask.switchNetwork(networkName): it changes the current selected network. networkName can take the following values: "main", "ropsten", "rinkeby", "kovan", "localhost".

  • metamask.confirmTransaction([{ gas, gasLimit }]): commands MetaMask to submit a transaction. For this to work MetaMask has to be in a transaction confirmation state (basically promting the user to submit/reject a transaction). You can (optionally) pass an object with gas and/or gasLimit, by default they are 20 and 50000 respectively.