The visual aesthetics in a modern application play a critical role in maintaining its user satisfaction and engagement rates. Some of the important parameters that are controlled by the visual elements include bounce rates and user retention rates. Bounce rates refer to the number of users who refrain from using the application after visiting it only once. The user interface elements play a critical part in maintaining the visual aesthetics of an application. By using visual regression testing, the application developers can maintain the proper placement and compatibility of all UI elements present in modern web applications.
So, with this article, we’re going to understand how app developers can initiate and execute automated visual testing with LambdaTest and Selenium. We will also discuss some of the best practices that can help boost the quality and efficiency of the testing environment.
The Basics of Visual Regression Testing and Integration of Test Automation
As we already mentioned earlier, the visual elements of an application are responsible for helping the user interact with the web app and navigate through it. These are some of the basic functions that must be available in all instances to avoid any breakdown. However, depending on the device screen size or resolution certain elements of a web application might change its position or refrain from working completely. So, to avoid any such unprecedented errors, the application developers must test the app thoroughly with the help of visual test cases.
Previously the app developers had to rely on a manual test bench as there was no alternative to verify these elements. However, with the integration of modern automation testing practices, it is possible to automatically conduct these processes with the help of human interaction emulation. The system will use a text file for supplying these required parameters and execute this process accordingly. Various modern automation test suits like Selenium and cloud-based solutions like LambdaTest support the integration of visual regression testing.
Introducing Selenium
Selenium is an open-source test suite for verifying the performance of modern web applications. Using multiple tools available with Selenium, the App developers can initiate automated testing on web apps. The Selenium core infrastructure has gone through 4 major updates that added more tools and improved the simplicity of the testing process. It is worth mentioning that the entire Selenium infrastructure is based on the popular programming language JavaScript. While using Selenium, the application developers can integrate libraries, agile methodologies, and various plugins.
Let us understand the core functioning of all the tools present under the Selenium Test Suit:
- The Selenium WebDriver is functional for initiating and executing the test cases in the native environment of the web browser. For this function, the Selenium WebDriver does not rely on a native compiler engine.
- Next, the application developers can initiate codeless automation testing with the Selenium integrated development environment. It analyses the user interactions and automatically generates the test cases in real-time.
- In case the app developers need to write the test cases manually, they can use the Selenium client API. With this tool, it is possible to write test cases in multiple programming languages and import them into the native environment of Selenium.
- Finally, while working with modern web applications, the application developers can utilize the Selenium Grid to conduct multiple test instances at the same time on different configurations and machines. It uses the principle of a hub that is connected to multiple nodes.
Integration of LambdaTest
Modern test cases heavily rely on the integration of real device testing for test accuracy. However, to avoid the expense of having a real device test lab, app developers can integrate cloud-based platforms in their testing environment. With these platforms, it is possible to utilize hundreds of real devices through remote servers that can be accessed on the Internet. A great example would be LambdaTest which removes location barriers, conducts real device testing, and maintains a real-time activity log.
With LambdaTest, it is possible to initiate and execute cloud-based automated cross-browser testing on web applications. The benefit of this process is that it guarantees stability irrespective of changes in browser version, operating system, or software parameters. LambdaTest can run the automation test scripts from not only Selenium but also other competitors like Playwright and Cypress. The significant advantage of using Selenium test cases is that LambdaTest can efficiently run it on more than 3000+ browser instances. The addition of real devices with thousands of emulation softwares crucially lifts the quality of the test reports.
Major benefits of using the LambdaTest real device clouds for visual regression testing are:
- The visual user interface testing cloud of LambdaTest is AI-powered. This means that this cloud can automatically identify all the UI elements present in a web application and test them accordingly.
- Moreover, the testing cloud of LambdaTest also allows the app developers to integrate the test cases with real devices to ensure pixel-perfect comparison for various resolutions, layouts, and sizes.
- Moreover, the process to integrate LambdaTest visual cloud is very simple as the developers can easily install it with the help of the npm package installer.
- With the help of the smart user interface, it is easy to work on the same branch and update the baseline branch. This process will automatically detect the changes for Git commands added to the baseline branch and compare them with non-baseline branches.
- It is also possible to seamlessly integrate continuous development and continuous integration with the LambdaTest testing cloud. It allows the developers to initiate and execute the development and testing processes simultaneously.
- Finally, it provides additional features like hyper execute, online browser testing, native app testing, and test range analysis for improving the speed and quality of the app development project.
Executing Automated Visual Regression Testing with Selenium and LambdaTest
With the help of certain prerequisites and a few simple steps, developers can easily initiate and execute automated visual regression testing with Selenium and LambdaTest:
- Setting up the Test Environment:
- To set up the testing environment, the application developers have to integrate the Selenium WebDriver with all the necessary programming languages. Some other languages that are supported by both Selenium and LambdaTest include C#, Java, Python, and many others.
- The next step in the setup process is to select the preferred programming languages, integrated development environment, or text editor. Eclipse can be a good choice depending on the requirements of the app developers.
- Creating the Automation Test Scripts with Selenium:
- Now the application developers have to write the Selenium test scripts that can interact with the user interface elements of web applications. It is important to remember the test cases will use the Selenium WebDriver for the execution process. Some of the common user interactions include filling out forms, clicking buttons, etc.
- Based on the requirements of the project, the app developers have to implement all the assertions for verifying the expected visual appearance of the app.
- Setting up the LambdaTest Account:
- The application developers have to navigate to the official website of LambdaTest and sign up for a new account in case they already do not have one.
- After this, the application developers have to log into their LambdaTest account and receive their access key which includes the username and the access token. The access key is critical to authenticate the test cases while using the LambdaTest cloud environment.
- Configuring the LambdaTest and Selenium Integration
- Based on the preferred programming language, the app developers have to import the required Selenium libraries along with the LambdaTest-specific configurations. It will help them to integrate the Selenium test scripts with the LambdaTest cloud. The following code will help to import the libraries with Python:
- from selenium import webdriver
from selenium.webdriver.common.by import By
from selenium.webdriver.common.keys import Keys
from selenium.webdriver.chrome.options import Options
# Replace <your_lambdatest_username> and <your_lambdatest_access_key> with your credentials
LAMBDATEST_USERNAME = “<your_lambdatest_username>”
LAMBDATEST_ACCESS_KEY = “<your_lambdatest_access_key>”
chrome_options = Options()
chrome_options.add_argument(“–headless”) # Optional: Run tests in headless mode for faster execution
desired_cap = {
“browserName”: “chrome”,
“version”: “latest”,
“platform”: “WIN10”,
“build”: “Visual Testing Example”,
“name”: “Selenium Visual Testing”,
“headless”: True,
}
driver = webdriver.Remote(
desired_capabilities=desired_cap,
command_executor=f”https://{LAMBDATEST_USERNAME}:{LAMBDATEST_ACCESS_KEY}@hub.lambdatest.com/wd/hub”,
)
- Setting the Visual Test Cases
- The LambdaTest testing environment will provide an API for initiating the visual test cases and comparing the test scripts of the web applications on multiple browsers and devices.
- The app testers have to capture multiple screenshots during the execution of the Selenium test cases. It is possible by using the LambdaTest visual testing API.
- Implementing the Visual Test Cases with Selenium
- The application developers must remember to capture the screenshots before asserting the visual appearance of the page. It will help them to have some live references while performing the comparison process.
- After this, the application developers will send the screenshots to LambdaTest and perform the comparison process using the baseline reference images.
- Analyzing the Test Reports
- Now all that is left is to allow the system to complete the testing process and generate the final report. The app developers have to go through this report to detect any bugs and errors that might be present in the code framework of the application. LambdaTest will highlight all the visual differences between the baseline and actual images captured during the testing process.
- The application developers have to continue reviewing the test cases and investigate all the discrepancies during the visual testing process and finally forward the application to the production phase. The Following Code will help to compare the screenshots:
import requests
# Replace <your_lambdatest_username> and <your_lambdatest_access_key> with your credentials
LAMBDATEST_USERNAME = “<your_lambdatest_username>”
LAMBDATEST_ACCESS_KEY = “<your_lambdatest_access_key>”
screenshot_file = “screenshot.png”
baseline_image = “baseline_image.png”
url = “https://api.lambdatest.com/automation/api/v1/compareScreenshots”
files = {“screenshot”: open(screenshot_file, “rb”), “baseline”: open(baseline_image, “rb”)}
data = {
“authToken”: LAMBDATEST_ACCESS_KEY,
“userName”: LAMBDATEST_USERNAME,
}
response = requests.post(url, files=files, data=data)
if response.status_code == 200:
result = response.json()
if result[“message”] == “Test Comparison Completed”:
if result[“imageDiffPercentage”] == 0:
print(“Visual test passed. No differences found.”)
else:
print(f”Visual test failed. Image differences: {result[‘imageDiffPercentage’]}%”)
else:
print(“Error in visual test comparison.”)
else:
print(“Error in API request.”)
The Conclusion
With this article, we aimed to improve our knowledge about visual testing with LambdaTest and Selenium. This is a very important parameter as the app development market will continue to become more and more dependent on automation testing practices. Other than test automation, the app developer should also constantly update their knowledge about this continually changing segment. It is also essential to conduct thorough market surveys so that the app developers can gather adequate information about the requirements of the target audience. Finally, it is very important to choose the correct tools that can complement the requirements of the app development project and also the developers.
