How to Begin with Puppeteer

How to Begin with Puppeteer


Puppeteer, let’s move on to a headless Chrome Node API! Puppeteer, a high-level API offered by the Google Chrome team, serves administrative needs. It enables us to provide real-time assistance to any Chrome DevTools Protocol-based browser. In a manner similar to a real browser, it also facilitates everyday operations. We’ll use Google Puppeteer to evaluate its many features and show how they may be combined to advance puppeteer testing.

Before we discuss how to use Puppeteer for end-to-end testing, let’s take a closer look at what it is and why it is so essential in modern web development.

Why Is E2E Testing Important and What Is E2E Testing?

Testing an application’s flow from beginning to end to see if it functions as expected is known as end-to-end testing. E2E tests identify system dependencies and ensure that the correct information is sent across various systems and system components. Automated end-to-end testing (E2E) simulates a user’s behavior while engaging with a program or browser. It guarantees the program’s smooth operation.

It becomes more challenging for development teams to manually test every component of functionality every time a new feature is ready to be deployed as web apps get more complex and feature-rich. By creating an E2E testing framework, people are relieved of the responsibility and ongoing task of evaluating functionality and putting it in machines that can run tests much more quickly and accurately each time.

Google Puppeteer: All the Information You Need

Puppeteer is far too simple to begin. It is easy since each release of Puppeteer ensures that the Chromium version of the headless Chrome component, provided voluntarily by the Chrome DevTools team, always functions.

Using Puppeteer, you can:

Sniffing websites

Create PDFs from websites. Explore a SPA to create web page screenshots using SVG and Canvas (single-page application)
To generate pre-rendered content, visit websites and extract data using the DOM API (server-side rendering).

Automatically submit forms

Similar to how Cypress uses Chrome extensions, automate performance analysis and UI testing.
Puppeteer installation requirements
Before using Puppeteer, you must understand JavaScript, ES6+, and Node.js. Installing the most recent Node.js version is required. To be more specific, Puppeteer needs Node at least version 6.4.0. Before proceeding, we must first download and set up one of Puppeteer’s packages. They include some of the following:

Book Package

Puppeteer-core, a compact library included in the library package, can be used with any browser that supports the DevTools protocol without installing Chromium. When utilizing this library in a project that connects with a browser remotely, and we don’t need to use a downloaded version of Chromium, for example, it’s convenient. To install, use the ‘npm install puppeteer-core’ command.

Packaged Goods

A complete browser automation solution is provided by Puppeteer, a sizeable package built on top of puppeteer-core. To install Puppeteer, use “npm install puppeteer.”
Browser Interaction
Puppeteer is merely a Chrome DevTools Protocol API, as was already stated. Because of this, the ecosystem of Puppeteer offers methods for starting fresh Chromium instances and connecting to already running ones.

launching the browser and establishing a connection to Chromium

Using Puppeteer to start a Chromium instance is the easiest way to communicate with the browser. Creating a sample and linking Puppeteer to it are the first steps in the launch procedure. You receive a browser instance that reflects our initialized instance and a Promise after the problem has been fixed.

Puppeteer and the newly formed instance are connected through the connect method. Now, we need to provide the WebSocket endpoint for our example. The Chrome launcher, on the other hand, merely shows you how to create an instance. You can connect a model in any way you wish if you have the required WebSocket endpoint.

Browser Context’s Function

Think about what would happen if we could use the same browser instance, but divide it up into different sessions that are all a part of the same shared browser instead of creating a new one each time. You can accomplish just that thanks to a session type called Browser Contexts. A default context is provided when a browser instance is created; However, different browser contexts can be built as necessary.

Along with demonstrating how to access each context, it is essential to understand that the only way to end the default context is to complete the browser instance, which also ends all of the browser’s contexts, allowing you to, for example, grant additional permissions without affecting the rest of the browser.

Full Head Mode

The headful option opens the browser with a graphical user interface throughout the instruction instead of the headless mode, which primarily utilizes the command line. In case you were wondering, the headless mode works best in environments that don’t call for or support a graphical user interface. Puppeteer’s key feature is that we can accomplish almost anything without using our minds.
Check for any errors during debugging.
We should be aware of the various available debugging options when programming. In the manual, you can find Puppeteer troubleshooting advice. Take a look at these fundamentals:

Looking at how the browser functions

We must investigate how our code interacts with the browser and what appears on the screen. We can accomplish this with the help of the headful mode, which we are accustomed to using. Additionally, while the browser is open, we can easily observe the operating instructions because the function “slowMo” slows down Puppeteer as it runs each task.

Application code debugging within the browser

You must open the DevTools and generally start debugging as you go if you want to debug the program in the currently open browser. It’s crucial to remember that utilizing DevTools immediately launches the DevTools and switches the browser to headless mode. Additionally, you can use “wait for target” to maintain the browser process until explicitly closing it.

The first method is simply a function that resolves a promise when “setTimeout” is finished. Some of you may be wondering if it’s possible to put the browser to sleep for a specific amount of time. On the other hand, the second method is less sophisticated yet calls for a page instance.

Fixing the Puppeteer-based procedure

We all know Puppeteer runs in a distinct Node.js process from the browser. As a result, debugging it should be done the same way you would for a typical Node.js application. The trick is to place the breakpoints right before Puppeteer performs its function, whether you connect to Puppeteer using an inspector client or ndb (a Node.js better debugging experience supported by Chrome DevTools). Additionally, you can add them programmatically by using the debugger; command.

Other Fascinating Characteristics of a Puppeteer

In addition to debugging Puppeteer, there are extra crucial elements to emphasize. Serverless applications or Docker containers can both be used to run Puppeteer. It can eavesdrop on network requests, compile performance data, and use a Chrome plugin to test them. On a mobile device, emulate Chrome to run code on a website. The Puppeteer has access to several additional items. The Google team is active enough to benefit developers in several ways.

The Interacting Puppeteer Page

We can build a single page or a collection of pages since the Puppeteer is associated with a browser instance that, as was previously stated, represents our browser instance. The class “page” denotes a browser tab or an add-on’s background. This class has valuable methods and events for interacting with the page, including selecting elements, obtaining data, awaiting items, and many more.

Code Coverage Use

With the code coverage tool, which is new in Chrome 59, you can check how much of the loaded code is used. The dead code can be reduced, which will shorten the time it takes for pages to load. Using Puppeteer, we can programmatically control the same feature. You can instruct Puppeteer to gather coverage data for the JavaScript and CSS files until the page loads. The function “calculateUsedBytes” may need to be defined to analyze the coverage data and determine how many bytes are used based on the coverage.

Performance Assessment

One of the objectives of online performance measurement is to examine a page’s performance during load and use it to speed it up. Let’s see how Puppeteer can be used to monitor the effectiveness of your pages.

Measures to assess load time

The ‘Window. The performance’ function has access to the Navigation Timing Web API, which provides data and metrics on page load and navigation events. The ‘evaluate’ function will eventually return undefined if given a process that generates a value that cannot be serialized. So, when evaluating, don’t forget to stringify “window.performance.”

Analyzing runtime based on metrics

In contrast, runtime metrics have a great API that Puppeteer offers to load time. JSHeapUsedSize displays the actual amount of RAM that the page is using. The outcome can be seen in the Chrome DevTools Protocol function Performance.getMetrics.

Investigating browser activity with tracer

Chromium Tracing is a Chrome profiling tool that lets you observe what the browser is doing in the background by focusing on each thread, tab, and process. However, it may be seen in the Timeline window of Chrome DevTools. This tracing ability is also available in Puppeteer, which, as one might anticipate, takes advantage of the Chrome DevTools Protocol.

For testing websites that are designed to scale quickly, LambdaTest is a platform that enables you to utilize Puppeteer to run headless tests on the fastest and most powerful test automation cloud in the world. More than 3000 distinct browsers and versions, including non-headless Chrome and Chromium, are available for testing.

Finishing up

The Google DevTools team developed Puppeteer, a complex tool, to simplify headless, automated browser testing. It starts up more quickly, has simpler syntax, and is helpful for more than just testing websites as they are being developed. Puppeteer provides an easy-to-use API and excellent abstraction, so we don’t need to worry about minute details.

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