It's hard without knowing your conditions when the app opens a new tab. It works perfectly fine for me. Here is a code demonstrating how I can use it. Read the comments to understand the steps.

UPDATED:

window.open() doesn't return a promise, thus browser.pages() is executed faster than the browser can create and report the event. We can use the targetcreated event to know if any new tab is created.

browser.on('targetcreated', function(){

    console.log('New Tab Created');

})

If you wait for a while or return a promise, you will see it reports it within browser.pages() count.

await tabOne.evaluate(() => {

    window.open('http://www.example.com', '_blank');

  });

await tabOne.waitFor(2000); // await for a while

console.log(current page count , (await browser.pages()).length); // 3

Here is the final code.

const puppeteer = require('puppeteer');



(async () => {

  const browser = await puppeteer.launch();



  browser.on('targetcreated', function(){

    console.log('New Tab Created');

  })



  // get current tab count

  console.log(current page count , (await browser.pages()).length); // 3



  // create a new tab

  await browser.newPage();

  // lets see if tab increased

  console.log(current page count , (await browser.pages()).length); // 3



  // use destructuring for easier usage

  const [tabOne, tabTwo] = (await browser.pages());



  // use the tabs aka Page objects properly

  await tabOne.goto('https://example.com');

  console.log(Tab One Title ,await tabOne.title()); // Example Domain



  // use the tabs aka Page objects properly

  await tabTwo.goto('https://example.com');

  console.log(Tab Two Title ,await tabTwo.title()); // Example Domain



  await tabOne.evaluate(() => {

    window.open('http://www.example.com', '_blank');

  });

  await tabOne.waitFor(2000); // wait for a while

  console.log(current page count , (await browser.pages()).length); // 3



  // close the browser

  await browser.close();

})();

If you run it, you'll get the result in following sequence.

/*

current page count  1

New Tab Created

current page count  2

Tab One Title  Example Domain

Tab Two Title  Example Domain

New Tab Created

current page count  3

*/