test.js

const puppeteer = require('puppeteer');

(async () => {
  const { HEROKU_EMAIL, HEROKU_PASSWORD } = process.env;
  const browser = await puppeteer.launch({headless: false})
  const page = await browser.newPage();
  await page.goto('https://dashboard.heroku.com');

  // login
  await page.type('#email', HEROKU_EMAIL);
  await page.type('#password', HEROKU_PASSWORD);
  await page.click('button[name=commit]');
  await page.waitForNavigation();

  await page.goto('https://dashboard.heroku.com/apps/cool-app3/logs');

  // wait for logs to show up!
  const element = await page.waitForSelector('.build-stream-output .build-stream-line');

  // read the log line
  const value = await (await element.getProperty('innerHTML')).jsonValue();

  // log out the log line for debugging
  console.log('value', value);

  // does it match what we expect?
  // in this case we have a canary app that only logs one thing
  if (/noisy-server/.test(value)) {
    console.log('success!');
  } else {
    console.log('dang no logs!!');
  }
})();