Introduction to Visual Testing with Playwright

testing

Some bugs can not be tolerated. You can just identify the bugs because some bugs are so obvious that anyone could see them. This is rare. As delivery constantly accelerates and the time spent manually checking and exploring the website decreases, we need a tool to reduce these risks. Here comes the visual testing. Visual automation testing helps identify and fix any visual defects to improve your web app experience and efficiency. 

Many tools are available on the market to perform visual testing, but Playwright is one of the most popular tools for this case. The Microsoft company initially developed Playwright, which has various features that help improve your visual testing efficiency.

In this article, you will see what visual testing is, what Playwright is, its various aspects, and a simple example of how to perform visual automation testing using Playwright.

What is a Playwright?

Playwright is a popular automation framework for end-to-end testing for modern web applications. Microsoft developed it, and its first version was released in 2020. You can also use the Playwright framework to perform single-page or multi-page application testing. Playwright has multi-platform support, allowing the testers to execute it on various operating systems such as macOS, Windows, Linux, etc. 

Hence, you do not need to write different code or modify the code according to the operating system. The playwright can do all this adaptation himself, freeing you from platform-related concerns. 

Apart from supporting various operating systems, Playwright supports multi-web browsers such as MS Edge, Chrome, Safari, etc. This compatibility across different web browsers allows the testing team to provide a seamless and smooth user experience for all types of users. Due to the support of various web browsers, it will enable you to select all the elements of the web application individually, and you can perform the software testing process over them by using the friendly API. 

Playwright allows you to create new browser pages and open multiple tabs using browsing context or the environment where relevant documents are presented to the user. Playwright for visual testing helps to get screenshots of each component at every stage of the testing process. Then, you can make an analysis based on visually comparing them. You can automate some real-time stuff for testing, such as scrolling, clicking, etc.

What is Visual Testing?

Visual testing for your website or web application is testing the visual components, primarily focusing on images and pixel comparison. Visual testing helps the team visually analyze your web components and make changes if required. When you run automated visual tests, it can recognize any visual differences in your web application due to the code changes. 

Suppose you have changed the CSS styling of a standard component, say default styling; it may significantly affect your web application. Visual testing helps identify the visual differences and errors in such cases and can detect unintended UI changes and prevent bugs from reaching end users. 

Visual testing is generally run to perform visual testing in the context of taking screenshots of the differences before and after applying the changes in the code to the web application. But it’s more than that. Visual tests also help simulate actions such as clicking and forming field entries. This is because visual tests often require the application to be pre-defined before the visual check can occur. 

For example, suppose there is an application that requires the user to log in to proceed with the further use of that application. It is a must-do step. By running the visual tests, you can enable the user’s authentication by writing a test script to ensure that the user must authenticate before using the application and navigate to the proper page. It will help that the web browser is in the appropriate state before executing a visual check.

Benefits of Visual Testing with Playwright

Now, let us look at the various points that show how Visual testing is essential in the website or web application automation testing process. These are:

  • Consistent UI/UX Stability: Visual regression testing helps test the web application’s visual components. Testing and rectifying the visual components improves the user interface and user experience (UI/UX). Also, visual testing with Playwright ensures reliability for users of various types of devices, resolutions, etc.
  • Early Issue Identification: Visual testing helps to detect the issues at the early development stage. Early defect detection helps tackle swift issue resolution, minimizing the chances of flawed features. In this way, visual automation testing improves the overall software performance and efficiency.
  • Cross-Platform and Cross-OS Support: Performing visual testing using Playwright helps detect and rectify visual errors. You can perform this visual testing with Playwright across various operating systems and devices. Other visual testing tools are available in the market but are not multi-language and multi-platform supporting. Playwright reduces the pressure of choosing preferred operating systems when used with cloud testing tools like LambdaTest.

LambdaTest stands out in automation testing due to its unique AI-powered test execution and orchestration capabilities. Unlike other platforms, LambdaTest offers users access to a vast grid of over 3000+ real browsers and operating system combinations. This diverse testing environment ensures thorough coverage, allowing for comprehensive testing across various configurations. It allows testers and developers to help resolve cross-platform issues by enabling cross-browser testing.

What sets LambdaTest apart is its ability to go beyond traditional automation capabilities. With its user-friendly interface and advanced features, LambdaTest empowers teams to seamlessly automate tests, enabling efficient and effective testing across browsers and operating systems. LambdaTest is a versatile and powerful tool for optimizing automation testing processes. The best part about testing over LambdaTest is that it allows you to perform web application testing and provides you platform to perform real device testing over the cloud.

  • Better Deployment: Regular visual testing instills confidence in software releases, decreasing the likelihood of unexpected visual regressions when rolling out updates or new features. 
  • Improved Testing Efficiency and Cost-Effective: Automated visual testing saves a lot of human effort and time, which is impossible in regular manual visual testing. Automated visual testing to remove defects with Playwright helps make your testing process effective and decreases the time for manual checks. 

Performing Visual Testing with Playwright

Let us see an example of how you can perform visual testing. The Playwright is a potent tool, and in this fast-growing tech era, you just need to make your application look impressive and detect and rectify any visual errors in your application. It helps to gain the attention of the users. Visual automation testing helps to make it possible to enhance the visuals of your application. 

Web applications sometimes contain dynamic content that may change after some time of use and interactions. These dynamic elements can pose challenges when performing visual testing; this is where the Playwright’s masking feature comes into play, allowing you to focus on the aspects that truly matter while ignoring the dynamic elements.

In this example, you will see masking in Playwright. Take an example of an application in which you have games and a carousel with images, which may be dynamic. As a tester, you want to take screenshots of the landing page while ignoring the dynamic pictures because they may change with time.


import { test, expect } from ‘@playwright/test’test(‘example test’, async ({ page }) => {  // Navigate to the specified URL  await page.goto(‘http://example.com’);  // Wait for network activity to stabilize  await page.waitForLoadState(‘networkable);  // Capture a screenshot while masking out a specific element  await expect(page).toHaveScreenshot({    maxDiffPixelRatio: 0.02,    mask: [page.locator(‘data-test-id=random-game-image’)],  });});;

In this example, 

  • The “expect(page).toHaveScreenshot” method captures the screenshots. 
  • Then we have the “maxDiffPixelRatio”. It defines the maximum allowed differences between the provided reference and captured screenshots.
  • Since it is masking in Playwright for visual testing, the “mask” option is used to direct the element that must be masked.

Limitations of Visual Testing

Visual testing is essential when we talk about removing the detects in the visual components of your web app. Although it is a potent testing technique, there are some points where visual testing cannot detect bugs and errors. In this section, you will see the limitations of visual testing and which areas visual testing cannot provide its use. They are as follows:

  • Security Testing: Security aspects of any web app or website are critical factors to consider. Security testing is done to verify the safety and security measures, such as identifying potential threats, vulnerabilities, weaknesses, unidentified access, etc. Any activity that may lead to security compromises must be recognized and fixed in the security testing of a web app. But Visual testing is not capable of providing security testing to us. 
  • Functional Testing: Functional testing is the application testing process to ensure the application’s working and functionality. It provides that the web app works by its specifications, ensuring that each feature, component, or interaction functions correctly and performs as intended, encompassing form submissions, user actions, data processing, and other essential operations. Unfortunately, Visual testing cannot perform functional testing for your web apps. 
  • API and Backend Testing: API and backend testing is the practice in which the testing team evaluates the functionality, working, and response of the various backend components of the application. The various backend components include APIs, databases, server-side operations, etc. So, you can not perform any backend or API testing while performing the visual testing. The reason is that visual testing focuses on the front end, requiring distinct methodologies to interact directly with and assess the backend systems and ensure their proper functioning and accuracy in handling data and operations.
  • Accessibility Testing: Accessibility testing ensures the application is accessible to all the target users without any issues. It is a significant factor that confirms compliance with accessibility standards like WCAG. Also, it focuses on features such as compatibility with screen readers, keyboard navigation, contrast adjustments, and other elements to provide the best possible user experience for a diverse array of audiences.

Conclusion

Visual automation testing with Playwright has several advantages, such as better platform support, multi-language support, and better development flow for your software web application. But there are also some limitations of visual testing as it is incapable of functional testing, backend and API testing, etc. 

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