Visual Regression Testing: A Comprehensive Guide

Visual Regression Testing

Table of Contents:

  1. Brief Introduction
  2. What is Visual Regression Testing? Why is it important?
  3. Use Case Scenario Of Visual Bugs
  4. How Visual Regression Testing Works?
  5. How To Implement Visual Regression Testing?
  6. How To Choose Visual Regression Testing Tools?
    • Automated or Manual?
    • Is your UI dynamic or static?
    • Does your team have time?
    • What is your build/release frequency?
    • How many bugs are slipping through?
  7. Conclusion

Brief Introduction

In today’s digital realm, user experience stands at the top to stand apart from the crowd. The amount of relatability and fine experience you can create for the customer decides your success. 

However, you may find the most well-crafted websites falling victim to elusive bugs or visual discrepancies. This leads to the potential customer getting frustrated and abandoning the website. 

Your website is a window to your brand. No matter how good you are in your services, inconsistencies in user experience can lead to unsatisfied customers. This is where visual regression testing enters the picture. 

It is a groundbreaking technique that allows developers to catch these bugs. In this blog, we will dive deeper into it, covering the what, why, and how. So let’s dive in.

What is Visual Regression Testing? Why is it important?

Visual regression testing, also known as UI testing, is a critical quality assurance process. It verifies the visual accuracy of websites and applications after code changes. 

It focuses on how users perceive and interact with the interface. Unlike functional testing, which checks functionality, visual regression testing specifically identifies visual defects. One that could impact the user experience.

Smooth transitions between various devices and resolutions are essential in today’s digital environment, especially when user expectations are high. Visual regression testing acts as a safety net. 

The method captures elusive visual issues that may go unnoticed during traditional tests. 

Angular visual regression testing detects problems like misaligned elements and broken layouts. It also detects overlapping text or images and responsive design failures. These minor issues can, in fact, impact user satisfaction, brand reputation, and conversion rates.

Additionally, visual regression testing streamlines development by catching visual defects early on. This reduces the time and effort spent on bug fixing later. 

It fosters collaboration between designers, developers, and QA teams. Moreover, it enables proactive maintenance of visual consistency and improved user experience. 

This stands to be some of the unmatched advantages of visual regression testing. Let us take a look at a use case scenario for a clear picture of the concept.

Use Case Scenario of Visual Bugs

Imagine a user opens a web app and tries to click a button, but they can’t because an ad covers most of it. This frustrates the user, and they wonder how the app developers missed such a glaring issue that affects their experience. 

They might even decide to delete the app because it prevents them from benefiting from it.

This situation is an example of a visual bug, an error that affects how users visually interact with software. Visual bugs are noticeable to users since they are the first things they see when using a website or app.

To address such bugs, visual testing automation plays a crucial role. In our interconnected world, numerous combinations of devices, browsers, and operating systems interpret code differently, leading to variations in how software appears. 

This is why the same software can look different or even appear scrambled on different devices.

Additionally, we must consider differences in screen sizes and resolutions. That’s why incorporating responsive design is essential in any development project. 

It ensures that the software adapts and displays properly across various devices. Consequently, this leads to a consistent user experience.

By utilizing visual testing automation and prioritizing responsive design, developers can effectively tackle visual bugs. They can enhance user satisfaction and optimize the visual experience for all users.

Now let us take a look at how this works for a clearer understanding.

How Visual Regression Testing Works?

Visual tests work by generating, analyzing, and comparing snapshots of web pages. This is in different browsers to identify any changes in pixels. These changes are known as visual diffs or perceptual diffs.

To conduct visual testing, you’ll need a test runner to write and execute tests and a browser automation framework. This is to simulate user actions. Developers write code that replicates user functions, like typing text into a field. It includes commands to capture screenshots at relevant points. The first time the test code runs, it records a set of baseline screenshots for comparison.

Once the baseline is set, the QA team runs the test code in the background. Whenever a change is detected, a screenshot is taken. Each screenshot is then compared to its corresponding baseline image. If there are differences between the images, the test is marked as failed.

Once the test code completes, an automatic report is generated. A reviewer examines the images that were identified as changed from their baselines. When testing tools are used, they provide reports that outline the differences between baseline images and final images.

If bugs are causing the image differences, developers can fix them and rerun the test to verify the fixes. 

If subsequent UI changes introduce discrepancies, developers review the screenshots and update the baseline images. 

These updated baselines, as a result, serve as the reference for future visual tests like that in cypress visual regression.

Now the question which must come to your mind is, how do we implement it? We cover that in the next section.

How to Implement Visual Regression Testing?

Incorporating automated visual regression testing into the CI/CD pipeline is highly beneficial. It saves time, reduces the chances of human error, and ensures the software maintains its visual appeal.

To begin, create testing scenarios that clearly define the elements to capture in screenshots and specify when to capture them during the test. These scenarios should encompass a range of user interactions, simulating real-world software usage.

Next, utilize an automated visual testing tool. This is to compare recent screenshots captured after implementing code changes with previously captured ones. The tool will generate a detailed report highlighting any differences detected between the two sets of screenshots.

Reviewers then examine the report to assess whether the introduced changes have produced the expected results or caused any disruptions. If you identify any bugs, fix them promptly or forward them to the relevant developers for resolution. 

Once fixed, update the new screenshot as the new baseline for future visual regression tests.

Now that we have understood the universe of this testing, let’s look at how to choose the ideal tool for it.

How to Choose Visual Regression Testing Tools?

When it comes to choosing the best open source visual regression testing tools, you have several options available. To make an informed decision, consider asking yourself the following questions:

Automated or Manual? 

Determine how often you want to conduct visual tests. For occasional checks, manual testing may suffice. However, if you want to ensure that no visual bugs slip through with every change, automated testing will be more efficient. 

Consider the tool’s learning curve and integration capabilities with your existing workflow for automated testing. 

Is your UI dynamic or static? 

Assess how frequently your user interface changes. For static pages, simpler tools can help spot visual bugs. However, if your pages have dynamic content that changes regularly, tools with advanced features like Visual AI may be better suited. 

For example- visual regression testing percy reflects these features.

Does your team have time? 

Consider the amount of time your QA team can dedicate to UI testing. If they have the capacity, dealing with potential false positives from pixel diff tools may not be an issue, or manual testing could be an option. 

However, for efficient testing, especially with large or dynamic applications, automated visual testing with Visual AI can save time.

What is your build/release frequency? 

Determine how often you run tests – infrequently, daily, or multiple times a day. If testing is infrequent, some inefficiency in test execution may be manageable. 

However, organizations conducting tests regularly or aiming to increase test velocity should prioritize tools that enable the QA team. This is to execute a large number of tests quickly.

How many bugs are slipping through? 

Assess the number of visual bugs that are escaping detection. With the growing complexity of web and mobile development, many teams experience more visual bugs than desired. In such cases, the value of automated visual testing becomes evident. 

However, if your team catches all bugs or is satisfied with the current level of bugs escaping, investing in open-source visual regression testing tools may not be necessary, at least for now.


We tried to give you a comprehensive guide to visual regression testing in this blog. By following it step by step, you will be able to nail your efforts in it.

We have tried to keep practical explanations and advice to provide something valuable, especially amongst so many confusing blogs.


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