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Streamline Your Testing Efforts: Automated Visual Regression Testing on LambdaTest



Streamline Your Testing Efforts: Automated Visual Regression Testing on LambdaTest

In the rapidly evolving field of software development, the top-notch web applications are vital for keeping ahead of the curve. The user experience, along with the user interface (UI), is important in assessing an application's success. A minimal discrepancy from the anticipated UI can result in an unfavorable user experience, subsequently affecting the reputation of the application.

Streamline Your Testing Efforts
Streamline Your Testing Efforts

Visual regression testing is an influential method for spotting unintended UI alterations that might arise from updates or modifications during the development phase. This technique ensures that the user interface stays uniform and visually attractive across various builds and platforms, allowing developers to identify and rectify unexpected changes that might have happened along the way.

LambdaTest, a digital experience testing platform, delivers automated visual regression testing. This technology empowers developers and testers to refine their testing processes and pinpoint UI regression defects effectively. In this article, we'll take you through an in-depth, step-by-step tutorial on using LambdaTest SmartUI for visual regression testing in tandem with Selenium. Whether you're a seasoned Selenium pro or a beginner, this guide will provide you with the essential skills to carry out successful visual regression assessments on LambdaTest. Nevertheless LambdaTest Visual Regression testing platform supports Visual Regression Testing with Cypress, Playwright, Puppeteer, K6, Storybook, and Appium.

Getting Started with Visual Regression Testing Using Selenium on SmartUI

Before we dive into the technical details, let's understand the importance of visual regression testing in software development. UI elements are crucial in providing an intuitive user experience. Any changes or discrepancies in the UI can lead to a negative impact on user satisfaction and may result in the loss of users. Visual regression testing helps ensure that the UI remains consistent and visually appealing across different builds, platforms, and devices.

LambdaTest SmartUI is an advanced platform that provides automated visual regression testing capabilities. It allows users to compare UI screenshots captured during different test runs to identify visual differences and potential UI regression bugs.

Prerequisites for Visual Regression Testing with Selenium on SmartUI

To get started with visual regression testing on LambdaTest SmartUI, it's essential to have a basic understanding of Selenium and Selenium WebDriver. Selenium is an open-source tool used for automating web browsers, while WebDriver is a critical component of Selenium that enables interaction with web browsers and execution of test scripts.

Next, you need access to the LambdaTest SmartUI platform. If you already have an account, you can log in using your credentials. If not, you can sign up for free and get access to LambdaTest's powerful features.

To establish a connection between your Selenium scripts and LambdaTest, you will need to access the Hub for Selenium remote connection. This connection allows you to run your Selenium tests on LambdaTest's Selenium Cloud Grid. Additionally, you will need to copy your LT_USERNAME and LT_ACCESS_KEY credentials from the Access Key button on the LambdaTest dashboard. These credentials will be used for authentication during test execution.

Step 1: Create a SmartUI Project

Creating a SmartUI Project is an essential step in organizing your testing efforts. A SmartUI Project acts as a container for all your builds and test runs related to a specific application or project. To create a SmartUI Project, follow these steps:

1. Go to the Projects page on LambdaTest SmartUI.

2. Click on the "New Project" button to initiate the project creation process.

3. Select the platform as "Web" to specify that you will be executing your Selenium tests.

4. Add a descriptive name to your project, specify approvers for any changes found, and add tags for easier navigation and organization.

5. Click on the "Submit" button to create your SmartUI Project.

By creating a SmartUI Project, you can easily manage and track your test runs and builds, making it convenient to organize and analyze test results.

Step 2: Configure Your Test with Selenium Desired Capabilities

With your SmartUI Project set up, you can now generate screenshots by running your automation scripts. To demonstrate this process, we will use a sample GitHub repository provided by LambdaTest: https://github.com/LambdaTest/smartui-node-sample.

In the repository's README.md file, you'll find instructions on setting up your LambdaTest credentials. You'll need to replace the placeholders with your actual LT_USERNAME and LT_ACCESS_KEY credentials to authenticate your tests with LambdaTest.

Next, edit the desired capabilities for your test suite. Desired capabilities are key-value pairs used to configure the browser, platform, and other settings for the test. In your Selenium script, you'll need to set the capabilities for the operating system, browser name, version, and enable visual regression testing.

Here's an example of how to set the capabilities in your Remote WebDriver DesiredCapabilities configuration:


let capabilities = {

  platform: "Windows 10", // Configure your OS for Selenium test

  browserName: "chrome", // Configure your Browser for Selenium test

  version: "latest", // Configure your Browser Version for Selenium test

  visual: true, // Enable visual regression testing for Selenium test

  name: "test session", // Name of the test for Selenium

  build: "Automation Build", // Name of the build for Selenium

  "smartUI.project": "<Your Project Name>", // Replace with the name of the project

  "smartUI.build": "<Your Build Name>", // Replace with the name of the Build

  "smartUI.baseline": false, // Enable if you want to update to a new baseline build


// Connecting to the LambdaTest Selenium Cloud Grid with Smart UI

let gridUrl =

  "https://" +

  "<Your Username>" +

  ":" +

  "<Your Access Key>" +


// Here is your Remote WebDriver Connection

let driver = await new webdriver.Builder()





With these configurations, you are ready to run your Selenium test with LambdaTest SmartUI's visual regression testing enabled.

Webhook for Taking the Screenshot

Now that your test is configured to capture screenshots, let's understand the purpose of capturing these screenshots during the test execution. Visual regression testing involves taking screenshots of the application UI at different stages of the test and comparing them against a baseline. Any differences found are flagged as potential regression bugs.

To capture screenshots during the test execution, you can use a webhook in your Selenium script. A webhook is a mechanism that allows different applications to communicate with each other in real-time. In this context, the webhook will trigger the capture of a screenshot at a specific point in your test.

Here's how you can attach the screenshot capturing webhook to the required segment of your Selenium script:


driver.executeScript(`smartui.takeScreenshot,{"screenshotName":"<Name of your screenshot>"}`)


This code segment will capture a screenshot during the test and associate it with a specified name. The screenshot will be used for comparison in the visual regression testing process.

After configuring the webhook, you can install the required dependencies and execute the test using npm and Node.js. By running the test, you will generate screenshots and initiate the visual regression testing process on LambdaTest SmartUI.

Once the test execution is complete, you can check the executed builds on LambdaTest SmartUI. This allows you to explore multiple features and execute more builds as needed.

Screenshot Capturing Options

LambdaTest SmartUI provides additional options for capturing screenshots, including the ability to capture full-page screenshots

 for websites with scrolling functionality on their application UI. Full-page screenshots are beneficial when you want to test the entire page layout, including the parts that are visible only after scrolling.

To capture a full-page screenshot, you can use the following webhook in your test cases:


driver.executeScript("smartui.takeFullPageScreenshot=<Your Screenshot Name>")


However, it's important to note that capturing full-page screenshots is supported for Selenium 4.0.0 with Chrome versions only. Ensure that the LambdaTest capabilities are updated in your project to execute full-page screenshots successfully.

Running Tests on Other Languages and Frameworks

In this section, we will discuss how to run smart visual tests on various programming languages and frameworks using Selenium WebDriver.

For NodeJS, we have already covered the process of configuring and executing the tests. The same process applies to other languages and frameworks. By executing the "smartui.takeScreenshot" command using Selenium WebDriver, you can perform visual testing on LambdaTest SmartUI for various languages like Python, Ruby, C#, and Java.

Here's an example of how to run visual tests on other languages and frameworks:


driver.executeScript(`smartui.takeScreenshot,{"screenshotName":"<Name of your screenshot>"}`)


By following a similar approach for different languages and frameworks, you can leverage the power of LambdaTest SmartUI's visual regression testing across a wide range of applications.

Fetching Screenshot Status and Results using WebHook

Once the test execution is complete, you may want to retrieve the status and results of the captured screenshots. LambdaTest SmartUI provides a webhook to fetch this information for analysis and reporting.

To fetch the status of the screenshots captured during the test, you can use the following webhook in your Selenium script:




This webhook will return the overall status of the screenshots captured during the test. The status can be one of the following:

- "Changes found": Indicates that visual differences were detected in the screenshots, suggesting potential regression bugs.

- "Match found": Indicates that the screenshots matched the baseline, meaning no visual regression bugs were detected.

In addition to fetching the overall status, you can also retrieve specific results for a particular screenshot by adding the screenshot name to the webhook:


driver.executeScript("smartui.fetchScreenshotStatus=<Your Screenshot Name>")


The fetched results will include details such as the screenshot name, URL, status, mismatch percentage, threshold, browser name, resolution, build ID, build name, and project name.

It's important to note that the webhook will return the result of the screenshot only after it has been processed, which may take a few seconds. To ensure accurate results, it's recommended to add a delay before fetching the screenshot results.

Advanced Options for Screenshot Comparison

LambdaTest SmartUI offers advanced options for screenshot comparison, providing users with more flexibility and customization for their visual regression tests.

1. Build Configuration: This option allows users to manage multiple screenshots in the same test suite and set a specific build as a baseline. It helps in comparing the changes across different test runs and ensures consistent behavior.

2. Advanced Test Settings: With this feature, users can customize the comparison of baseline and test output screenshots. It provides options for fine-tuning the comparison process, such as adjusting the color threshold and ignoring specific types of changes.

3. HTML DOM Config and Options: Sometimes, there might be dynamic elements on a page that change their position across different test runs. This feature allows users to ignore or select specific areas on the page for comparison, ensuring accurate results even with dynamic elements.

These advanced options empower users to optimize their visual regression testing and obtain reliable and actionable results.


Visual regression testing is an indispensable aspect of modern software development. It helps ensure that web applications maintain their desired appearance and functionality, even after code changes or updates.

LambdaTest SmartUI provides an efficient and automated solution for visual regression testing, enabling developers and testers to streamline their testing efforts and detect UI regression bugs early in the development process. By following the step-by-step guide provided in this blog, you can leverage the power of LambdaTest SmartUI and Selenium to conduct successful visual regression tests.

With features such as SmartUI Projects, webhook for capturing screenshots, and advanced options for comparison, LambdaTest SmartUI empowers developers and testers to deliver top-notch web applications with confidence.

So, why wait? Start streamlining your testing efforts with automated visual regression testing on LambdaTest SmartUI today and elevate the quality of your web applications to new heights. Happy testing!

We hope this step-by-step guide has been valuable in understanding the process of visual regression testing using LambdaTest SmartUI and Selenium. If you have any questions or need further assistance, feel free to leave a comment below. We would love to hear from you and assist you in improving your testing efforts! Thank you for reading, and we wish you all the best in your visual regression testing journey.

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