What is Parallel Testing? (Definition, Approach, Example)

Most companies, especially the one who develops small-sized applications are still ignorant to parallel testing. However, what these companies don't comprehend is the future is changing dynamically. Nowadays, users want an extensive range of functions in a single application. To cater to users' demands, you are bound to expand your applications in the coming times. When the stakes are high, and time-in-hand is low, then parallel testing is the answer.

This article attempts to give you a fair idea about the importance of parallel testing, its implementation, and how it can change the landscape of testing solutions.

What is Parallel Testing?

Parallel testing is a semi-automated testing process that focuses on cloud technology and virtualization. It allows you to test several configurations of an app at the same time. The primary goal is to build a robust and budget-friendly product at a small time frame without compromising in quality.

You can run parallel testing on a single application or several components on multiple platforms. It allows you to test the app, subcomponents such as OS, browsers, or even both.

You can use both real and virtual testing machines for this test. However, parallel testing is commonly used on separate virtual machines within the cloud. Regardless of what testing medium you choose, parallel testing allows you to run more tests than sequential testing.

It is considered a semi-automated testing process because you may execute it using manual and automation techniques. For example, you need a dedicated tester for the manual part, whose work is to interact with the application through the main computer. In the automation phase, the software under test connected is set to run automatically and test several test environments without any human interaction.

Example of Parallel Testing

Let's give you an idea of sequential testing before moving to parallel testing.

Let's assume you have written an automation test script to check the functionality of the sign-in form of your web application or site. You want to execute this test on more than fifty browsers and various OS combinations.

Assuming each test runs for 2 minutes, it would take 120 minutes to complete the whole test process. Now, remember that it takes up to 2 hours to test only one module. Imagine how much time it will take if you perform the test on all modules such as pricing, contact form, transaction, and other site functionalities.

Even if you automate the process, it will take a lot of time to complete the test in sequential testing as you have to run them one after the other.

Now, with parallel testing, you can run 'n' numbers of parallel tests simultaneously. For example, if you decide to run three tests, the execution time will be cut down to 40 minutes from 120 minutes. Similarly, it will reduce to 30 minutes if you run four tests simultaneously and so on.

Importance of Parallel Testing

Following are the benefits of adopting parallel testing as your primary testing approach −

  • Extend your test coverage − Parallel testing allows you to run a wider scale test compatibility within a short duration. For instance, if you want the 'order placing' function of an application, you can run it on different OS, browser, versions, etc., in just one go. Unlike sequential testing, you don't have to run a test repeatedly.

  • Reduces your test duration − You can test unlimited concurrent tests in parallel testing simultaneously. While in sequential testing, you can run only one test at a time. In short, the time takes to run hundred test modules (assuming) will be equal to the time taken to execute one in sequential test. It goes without saying, you will be able to complete the project way faster than ever.

  • Reduces your cost − Since parallel testing runs on the cloud, it will cost you significantly less than sequential testing. As, in the latter, you have to pay for developing, maintaining, and upgrading the test environment, ending up paying a fortune.

  • Enhances continuous integration and delivery − To establish continuous integration and delivery is a process you need to keep the functional tests frequently running at a rapid pace. Since you can run these tests in parallel, it will give you enough time to prepare quality test data. You can send detailed reports to the respective teams to work on the issues faster and better.

  • Continuous Testing − Implementing a continuous testing process in sequential testing is impossible since continuous testing requires a faster test cycle. Instead of physical hardware and systems, parallel testing runs on cloud technology and virtualization. It allows you to perform large-scale tests faster and release them in the market as earliest as possible.

Preparing a Parallel Test Case

It's best to develop individual projects for browser compatibility that includes testing various web application functionalities. It should be followed by creating a master project to test those different projects.

Parallel testing is divided into two-level criteria- Entry-level and Exit Level.

In the entry-level criteria, you need to define specific tasks and ensure their quality before introducing them in the parallel test process.

  • Make sure to prepare the proper testing environment

  • Defines all pre-conditions and scenarios before executing the test

  • Kindly ensure new data and legacy data are properly migrated

The exit level criteria define the steps to perform parallel testing perfectly.

  • Starts by running old system against new systems

  • Know how both systems are different from each other

  • Use the same input to run it through a complete testing cycle

  • Measure the output of the newly developed system to the old one

  • Report bugs to the concerned team


As organizations are shifting from manual testing to automation, testing solutions are becoming more agile and scalable nowadays more than ever. However, running multiple tests in parallel remains one of the most problematic areas in automation testing. Most businesses are still following sequential testing methods for quality assurance, leading to more time, effort, and resources.

Parallel testing is a convenient and faster way to deliver quality applications without compromising their quality. Besides that, it also allows you to save money that you would be spending on developing and maintaining a full-scale test environment.

Updated on: 20-Aug-2021


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