In today’s fast-paced digital world, efficient testing techniques have become crucial. Every organization ought to ace the industry competition with top-class software development. In the present scenario where time is of the essence, it has become essential to furnish economical and competitive software while fulfilling the current industry and end-user demands. One of the most effective methods of testing software applications is through automation testing using Selenium.

Selenium is a widely utilized open-source tool for automating web browsers. It authorizes software testers to execute tests across different browsers and platforms effortlessly. Parallel testing is a technique that facilitates software testers to run multiple tests simultaneously. It can enormously diminish the time required for testing. Parallel testing with Selenium can help software testers to accomplish speedy and more efficient testing. This eventually results in a better-quality software application.

What is Parallel Testing?

Parallel testing, also known as parallel test execution, refers to a software technique that leverages automation testing abilities to execute the same tests simultaneously in multiple environments, browser configurations, and real devices. It can significantly diminish the time and effort of testing. In parallel testing, two different software versions are executed parallelly with the same input. The objective behind this process is to determine whether the new system and the legacy system are responding similarly or differently.

Parallel testing primarily aims to save resources and time. It facilitates the tester to ensure that the system retains the required ability to run the software efficiently. Parallel testing primarily aims to save resources and time. It facilitates the tester to ensure that the system retains the required ability to run the software efficiently. Also, the testing can be performed either by manual means or with test automation tools.

Parallel testing is different from sequential testing. In sequential testing, different modules or functionalities are tested one after the other. When testing applications across multiple browsers, it is common practice to perform tests one browser at a time in a sequential manner. This approach to testing is tedious and resource-intensive.

Parallel Testing in Selenium

Selenium Grid authorizes testers to run tests in different environments and browsers concurrently. It assists in executing automated cross-browser testing simultaneously across various browsers and their corresponding versions. The primary goal of executing parallel testing is to diminish the overall time, effort, and resources for testing while ensuring that the quality of the product is not compromised.

One of the best practices for executing parallel test execution is to create different projects for the testing of browser compatibility in different parts of the web applications and a master project for testing the myriad projects. To execute parallel test execution in Selenium, there are two-level criteria, entry-level and exit-level criteria.

Entry-Level Criteria

In entry-level criteria, specific tasks are determined that ought to be achieved before running the tests in parallel. These tasks incorporate:

  • Establishing a testing environment layout before starting parallel test execution in Selenium. 
  • Migrating legacy and new data successfully.
  • Specifying pre-conditions and scenarios before commencing the automated browser testing technique.

The Exit Level Criteria

Exit level criteria define the measures for executing the parallel test execution successfully. This includes:

  • Executing old systems against the newly developed systems.
  • Comprehending the differences between old systems and new systems.
  • Driving through the automated browser testing process while employing the same input. 
  • Assessing the outcome of a newly developed system in comparison to the old system.
  • Reporting the bugs and issues, if any, to the software development team.

Best Practices for Parallel Test Execution

To attain the desired results from parallel test execution, consider the following tips to improve the testing outcomes.

Having Cloud Infrastructure in Place:

Running parallel test execution on local infrastructure can be extravagant. Organizations need several software, hardware, and mobile devices to execute tests simultaneously. On the other hand, the expenses associated with public cloud infrastructure are determined based on usage. In cloud-based testing environments, the quality assurance team can utilize multiple virtual machines to execute test scripts on diverse configurations concurrently and subsequently deactivate them. There are no ongoing expenses associated with this, and though usage is frequent, it is of shorter duration.

Leveraging parallel testing with Selenium becomes truly powerful when combined with a cloud-based platform such as LambdaTest. This AI-powered test orchestration and test execution platform significantly increases testing efficiency as it allows for parallel test execution in Selenium. LambdaTest gives access to 3000+ browser and operating system combinations; you can run multiple tests simultaneously, reducing test time and accelerating the software release cycle. LambdaTest’s Selenium online Grid facilitates scalable Selenium testing, leading to increased test coverage and a faster feedback loop.

Executing Autonomous Test Scripts:

In parallel testing, it is imperative that each test operates independently and does not rely on the outcome of another test. By employing autonomous 

test scripts, QA professionals can minimize the occurrence of blocked tests during a test run.

Reviewing and Optimizing the Test Suite:

Oftentimes, testers have a desire to include every possible test case to augment test coverage. Nevertheless, to enhance the effectiveness of parallel testing, it is crucial to prioritize the test cases. It is imperative to select tests that encompass the areas of the application that are at higher risk in terms of code complexity and critical functionalities.

Focusing on Data Management:

Effective test data management is a critical factor for successful parallel testing. It is essential to start with a well-defined strategy that includes two primary components: a creational strategy for generating test data and a cleanup strategy for removing it. However, the pivotal aspect is to tailor the strategy to a specific case.

Avoiding Hard Code Values:

A lot of testers follow a particular testing sequence that is hard-coded into the source code. Nevertheless, this approach creates dependencies between test cases and limits the ability to run tests in parallel effectively. It is recommended to avoid hard-coding values to ensure each test is independent and can be executed as required. Testers can also consider implementing a data-driven approach in their testing framework to configure test cases.

Be Strategic and Prioritize:

Parallel testing, while facilitating multiple tests to be conducted simultaneously, still has limitations on the number of tests that can be run simultaneously. To increase test coverage, prioritize test cases instead of running every test case. Choose tests that cover critical functionalities and code complexity in the application’s risky areas. It is essential to note that parallel testing should not be viewed as a license to run unlimited tests.

Benefits of Parallel Testing
Benefits of Parallel Testing

Benefits of Parallel Testing

Parallel testing is reliant on the utilization of cloud-based virtual machines, facilitating the testing time to be divided by the number of test machines utilized. As a result, testing duration can be diminished significantly compared to traditional sequential techniques. Nonetheless, the advantages of parallel testing are not limited to time-saving attributes. 

The primary benefits of parallel testing encompass the following:

Increase Test Coverage: Parallel testing provides access to more than 2000 devices, configurations, and platforms in the cloud. This helps in improving the coverage range of testing. You can create a single test on the local machine and execute that test in parallel in any Windows or macOS browser, including Chrome, Microsoft Edge, Internet Explorer, Firefox, and Safari. If the application is compatible with mobile browsers, it can be tested uniformly across supported browsers on all iOS and Android devices.

Reduce Testing Expenses: Running tests in parallel significantly diminishes the cost per test. Providing testers with instant access to updated browsers and devices through cloud technology eliminates the need for them to maintain an internal infrastructure for browsers and devices. Parallel test execution authorizes garnering the advantages of having various browsers and device combinations to ensure the expected performance of the application.

Optimizing CI/CD Processes: Parallel testing is a compatible approach for continuous integration and delivery. It enables teams to execute tests immediately after developers submit code updates during the entire software development lifecycle. Timely reporting and prompt feedback facilitate clear communication and collaboration among different departments within the organization.

Affordability: Acquiring leasing time for testing on cloud services is a cost-effective solution than constructing and upholding an internal testing infrastructure. Moreover, utilizing cloud-based testing grids authorizes running tests with a high degree of concurrency, which significantly lowers the cost per test.

Improvement of Testing Practices: Parallel testing presents a promising opportunity to enhance the quality assurance procedures within an organization. By leveraging high-speed testing, various tests can be conducted within a shorter timeframe, facilitating the QA team to refine testing methodologies, identify bugs promptly, and uncover potential vulnerabilities with greater efficiency.

Limitations Of Parallel Testing

Parallel testing provides various advantages. Nevertheless, it is also paramount to acknowledge and assess the limitations it presents. Here are some limitations of parallel testing that necessitate careful consideration:

  • Inter-dependent tests
  • Flaky tests
  • Multiple browser issues
  • Data dependencies
  • Infrastructure limitations


Parallel testing is recognized as a highly efficient technique that empowers developers and testers to establish a more effective CI/CD pipeline while reducing risks, efforts, and costs. Parallelization has played a crucial role in reducing QA expenses by executing test cases with high concurrency and constant improvements in scripts to yield more accurate results.

The current market offers a multitude of parallel testing toolkits that facilitate the utilization of this testing approach and streamline the entire software development life cycle.

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Lisa Freire is a versatile writer with a passion for exploring a wide range of topics. From the latest tech trends and digital marketing insights to business strategies, lifestyle tips, SEO hacks, travel adventures, and gaming reviews, Lisa's diverse expertise shines through in her articles. With a knack for simplifying complex concepts and a commitment to delivering valuable content, she aims to keep readers informed, inspired, and entertained across various subjects.


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