Book Image

UI Testing with Puppeteer

By : Dario Kondratiuk
Book Image

UI Testing with Puppeteer

By: Dario Kondratiuk

Overview of this book

Puppeteer is an open source web automation library created by Google to perform tasks such as end-to-end testing, performance monitoring, and task automation with ease. Using real-world use cases, this book will take you on a pragmatic journey, helping you to learn Puppeteer and implement best practices to take your automation code to the next level! Starting with an introduction to headless browsers, this book will take you through the foundations of browser automation, showing you how far you can get using Puppeteer to automate Google Chrome and Mozilla Firefox. You’ll then learn the basics of end-to-end testing and understand how to create reliable tests. You’ll also get to grips with finding elements using CSS selectors and XPath expressions. As you progress through the chapters, the focus shifts to more advanced browser automation topics such as executing JavaScript code inside the browser. You’ll learn various use cases of Puppeteer, such as mobile devices or network speed testing, gauging your site’s performance, and using Puppeteer as a web scraping tool. By the end of this UI testing book, you’ll have learned how to make the most of Puppeteer’s API and be able to apply it in your real-world projects.
Table of Contents (12 chapters)

Tracing Pages

In this section, we will cover how to get performance information using the tracing object you can find on the page.tracing property. I saw this question more than once on Stack Overflow: How can I get the Performance tab's information using Puppeteer? The answer is: You can get all that information from the tracing result. There is a high chance that you will get a reply like: "Yes, I say that, but the result is too complex." And yes, the tracing result is quite complicated. But we will try to see what we can get from that object in this section.

If you open DevTools, you should see a Performance tab like this one:

Performance tab

As you can see, the Performance tab is not processing information all the time because it's a costly process. You need to start "recording" the tracing, Chrome will begin collecting lots of data from the browser, and then you have to stop the tracing process.

If you click on the second...