Visual regression testing.

Visual regression testing ensures that any changes you make to your site don’t interfere with the existing structure, features, or interface. Without being a visitor on your own website, you’d otherwise remain ignorant to any disruptions like visual bugs or unresponsive content.

However, with visual regression testing, you can spot issues before they cause problems for your users. This way, you can make sure your site looks great and that all User Interface (UI) elements are working correctly. Better yet, you can find automated tools to make this easier. ⚙️

In this post, we’ll take a closer look at visual regression testing. Then, we’ll discuss some benefits and show you how to implement it on your website. Let’s jump right in! 🦌

📚 Table of contents:

An introduction to visual regression testing

As we’ve mentioned, visual regression testing verifies that your website looks and behaves in the way you expect. Plus, it ensures that there have been no unintentional visual or functional changes.

Typically, visual regression tests work by comparing a baseline screenshot of your web page with a current, up-to-date version of your web page. Then, you can manually pick out the differences or install an automated tool to spot the differences.

There are many kinds of issues that these visual tests identify. Most commonly, you can catch visual bugs that go unnoticed in regular functional tests. These bugs might result in misaligned content, overlapping images, rendering issues, or partially visible elements.

While visual regression testing is a key part of website maintenance, it works best in conjunction with usability testing and functional testing. In particular, visual regression testing is very important for websites that place a strong focus on the User Experience (UX) or that update frequently. 🖱️

The benefits of visual regression testing

There are several benefits to implementing visual regression testing on your website. First off, these kinds of tests can pick up on the most subtle issues with your interface, enabling you to improve your UX.

This is especially helpful because visual bugs are notoriously difficult to detect unless you visit your own website on the front end. As such, it lets you replicate real-world scenarios like testing buttons, pathways, and more.

Better yet, it’s a low-cost way to conduct visual testing on your site. And, as we’ve discussed, you can install automated tools that capture snapshots of your website at regular intervals. This makes the process super convenient and easy to maintain.

Lastly, visual regression tests can help you improve your mobile experience since you can pick up on issues that are exclusive to mobile or tablet displays or even specific browsers. 🌐

How does visual regression testing work?

Visual regression testing compares screenshots of your UI to detect visual issues. However, there are different methods that you can use.

First off, developers can run manual visual regression tests, which involve scanning pages and checking for visual defects. This can be time-consuming, and human error can also be a drawback. However, it can be useful in the early stages of website development.

On the other hand, you might prefer the pixel-by-pixel comparison method. In this instance, your automated tool compares the screenshots and analyzes them at a pixel level. Then, if a discrepancy occurs, you’ll be notified of the issue.

The downside of this method is that you might identify cases that are irrelevant for usability. Plus, it can result in false positives unless you use a tool that factors this into the equation.

Another popular way to conduct visual regression tests is to make DOM-based comparisons. This method relies on the Document Object Model (DOM) and monitors your site before and after a change is made.

This way, you can discover DOM code alterations, but it isn’t a truly visual comparison. As such, it might yield false positives when the code doesn’t change but the UI does, like with dynamic or embedded content. Therefore, it’s important to review the test results to ensure no visual bugs have gone unnoticed.

Lastly, you can conduct visual regression tests using visual Artificial Intelligence (AI). By using a well-trained AI assistant, you can pick up on visual errors in the same way that a human can. This eliminates the false-positive issue that limits alternative methods and enables you to test dynamic content. 🤖

How to implement visual regression testing on your website

If you want to implement visual regression testing on your website, there are a few factors to consider. For instance, if you only want to conduct tests occasionally, manual testing can be a good option. However, if you want to run tests after every change on your site, an automatic solution makes sense.

Additionally, if your UI doesn’t change too often, simple tools will suffice. But for frequently updating websites, you might require a more sophisticated testing tool. You’ll also need to consider cross-device and cross-browser validation.

If you decide to install an automated visual regression testing tool, you can find free, open-source options. Or, if your budget allows, you can purchase premium plans.

For instance, Selenium and Cypress support visual tests and generate screenshots of your web pages. Meanwhile, Percy makes it easy to manage the testing process and helps you avoid false positives.

If you run a WordPress site, you can install a plugin like VRTs – Visual Regression Tests which conducts automatic daily tests for selected pages or posts:

Then, once you’ve chosen a testing tool, you can create testing scenarios where you’ll define what you want to capture and configure several other settings.

At this point, you’ll use the platform to compare recent screenshots against the baseline screenshot, and the tool will usually generate a report that lists the differences. If any bugs are identified, you’re able to fix them (or send them to a developer). Then, you can update the new screenshot as a baseline for all your future tests. 👨‍💻

Conclusion 🧐

Visual regression tests provide an easy way to keep your UI free from visual bugs and other issues that might disrupt your UX. Typically, it works by taking snapshots of your web pages after changes are made.

Then, these snapshots are compared against a baseline version to detect visual errors.

Better yet, there are various methods to suit the needs of your website. For example, you can conduct manual tests or AI tests. Plus, you can compare snapshots at the pixel level or make DOM-based comparisons. Then, you’ll set up testing scenarios to identify issues that need to be fixed. 🔧

Do you have any questions about how to implement visual regression testing on your website? Let us know in the comments below!

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