The Comprehensive Guide to Parallel

Parallel Testing - As the complexity of applications increases, traditional sequential testing methods may become a bottleneck, resulting in longer test cycles and delayed releases. Parallel testing can slash test execution time and boost efficiency like never before.



In today's fast-paced software development landscape, where time is of the essence, efficient testing practices have become more crucial than ever. Traditional sequential testing methods can be time-consuming, leading to delays in project delivery. That's where parallel testing comes in as a game-changer.

Parallel testing is one such powerful solution to optimize your testing efforts. By harnessing the potential of parallelism, software testers can dramatically reduce test execution time while maintaining the same level of test coverage.

In this guide, we'll discuss everything you need to know about parallel testing. Let's get started.

What is Parallel Testing?

In parallel testing, tests are run simultaneously in different environments, devices, and browser setups. It primarily aims to save time and resources. It is contrary to serial testing, where tests are run one after the other, which can be time-consuming, especially for large test suites.

Testsigma′s introduction to Parallel testing

What is not Parallel Testing?

Up until now, our focus has solely been on parallel testing. However, knowing the opposite is also necessary. Let’s look at some examples where the testing process is not parallel testing.

  • Testing only one software or multiple features with dependencies on each other.
  • Running cross-browser or cross-device testing.
  • Executing two versions of software one after the other instead of running them simultaneously.

When to Perform Parallel Testing?

Below are some example scenarios:

  • When data is being imported from an older system to a new one, parallel testing can be highly beneficial. They help ensure that the data transfer is seamless by using an automated regression test suite.
  • When there is a new update for an application that is similar to the previous version, parallel tests can be run to verify different versions of the application. This helps ensure that the new update functions properly and remains consistent with the earlier version.
  • When importing legacy data from an old system to a new system or a different company, parallel tests can be used to validate the successful transfer of data. By running tests concurrently, any issues or discrepancies can be identified more efficiently.
  • When testing a software application across different devices, operating systems, and browsers, parallel testing is useful. It allows for simultaneous testing on multiple platforms, ensuring compatibility and functionality across various configurations.

Parallel Testing Example

Imagine you have an automation test script that checks the sign-in form of your web application. You want to test it on more than fifty different browsers and operating system combinations.

Running these tests sequentially would take around 2 hours to complete testing just one module (the sign-in functionality). And if you have multiple modules like pricing, contact form, and transactions, the testing time would increase significantly.

However, with parallel testing, you can run multiple tests simultaneously. Let's say you decide to run three tests simultaneously. The total execution time would be reduced to one-third of the previous time, that is, about 40 minutes, instead of 2 hours.

By running more parallel tests, like four or more, the time required for testing continues to decrease. For example, with four parallel tests, it would only take around 30 minutes.

In simple terms, parallel testing allows you to run multiple tests simultaneously, saving a lot of time compared to running them one after another.

Why do Parallel Testing: The advantages

The major reason for parallel testing is to save time. But there are other key advantages too, including,

1. Increases Testing Speed

Sequential testing can be very time-consuming. But, parallel testing speeds up the testing process by running multiple tests simultaneously.

2. Saves Time and Reduces Costs

Using parallel testing, you can test your application across multiple browser and device combinations at the same time. It helps reduce the testing cost. Also, testers can use cloud-based resources instead of having an in-house infrastructure, which can be costly and time-consuming.

3. Increases Test Coverage

Parallel testing helps achieve better test coverage in less time. One example is cross-browser testing. Like when using a cloud-based test platform like Testsigma, you can execute your automated tests on cloud lab that give you access to over 3000+ real devices and tablets and 1000+ browser/OS combos. It makes your test fast and increases test coverage as you can test every possible scenario.

4. Optimizes Your CI/CD Process

Parallel testing is crucial for continuous integration and delivery. It enables running tests simultaneously, allowing developers to test new code updates promptly throughout the SDLC. It offers timely reporting and swift feedback and enhances communication across different departments.

5. Improvement of Testing Practices

It helps improve the QA routine in your organization because testing at high speed will allow them to test more.

How to Approach Parallel Test Creation?

The approach you take to create parallel tests clearly depends upon your project needs. Suppose you need to run parallel tests for cross-browser compatibility. One way is to develop a suite of projects within a master project, each of which will have its entry and exit criteria. Understandably, the master project also consists of entry and exit points.

Entry points need to be fulfilled before starting the parallel test execution:

  • Identify the test suites for parallelization and understand application architecture.
  • Determine which parallel testing framework will be good for your project.
  • Define the necessary pre-conditions and test scenarios suitable for automated browser testing.

Exit points must be satisfied to mark the tests complete:

  • Validate the parallelization strategy by ensuring that parallel execution provides the expected benefits.
  • Verify that synchronization mechanisms effectively manage shared resources and prevent conflicts during parallel test execution.
  • Conduct an exit review with relevant stakeholders to assess the success of parallel test creation.

Challenges of Parallel Testing

While parallel testing offers numerous benefits, it also comes with certain limitations that should be considered. Here are some of the key limitations of parallel testing,

1. Inter-dependent Tests

When a test relies on the completion of another test, you can not run parallel tests. This limitation arises when you wish to avoid starting a test if a previous test has failed. In such cases, it is important to address the issue that caused the failure before proceeding with additional tests to save time and resources.

2. Data Dependencies

Parallel testing can become challenging or impossible when multiple tests need access to the same data. This is because each test will attempt to fetch or modify the data simultaneously. Parallel tests must not have dependencies on the same data.

3. Infrastructure Limitations

If your infrastructure has a limited capacity for handling tests concurrently, you need to limit test parallelization. Trying to run more tests simultaneously than your infrastructure can handle will lead to test failures and inconsistencies due to insufficient resources.

4. Multiple-browser Issues

Though parallel testing allows testers to perform cross-browser testing, its test coverage of various browsers is much more restricted.

Other challenges include:

  • Testers should focus on the data input and product flow
  • Platform limitations like the CI/CD platform could limit test parallelization.
  • It requires complete product knowledge.

Best Practices for Parallel Testing

To ensure your parallel testing is effective, follow the below best practices,

1. Run Autonomous Test Scripts

It is vital to create autonomous tests. Each test should be independent and not rely on the outcome of another test. It is because parallel tests will need to be executed simultaneously.

2. Set Up Cloud Infrastructure

For parallel testing, you will need multiple hardware/software devices for test execution. Investing in all these devices could be costly. Instead, it is recommended to choose to invest in a public cloud infrastructure that would host these devices and provide them as a service.

3. Test One Feature at a Time

Testing one feature at a time is beneficial as it helps you quickly identify failures. This approach is crucial for maintaining the performance of a CI/CD pipeline. Instead of testing multiple features together, focus on individual features, ensuring that any failures are detected promptly.

4. Avoid Using Static Objects

It is best to avoid using static objects because they can create conflicts when multiple tests are run simultaneously, as one test may interfere with the object while another tries to manipulate it.

5. Keep Tests Similar in Length

It is essential to design tests that have similar durations. It helps ensure that all tests finish around the same time, avoiding situations where most tests are completed while waiting for one slow test to finish.

6. Be Strategic & Prioritize

Although parallel testing allows multiple testing simultaneously, there are still limitations on how many tests you can run at once. Instead of running every test case to increase the test coverage, prioritize the test cases.

Choose the tests that cover the risky areas of the application in terms of critical functionalities and code complexity. Remember, parallel testing is not a license to run unlimited tests.

7. Resetting the test data

To prevent cross-contamination of data, test data should be created, used, and removed. It ensures that the system remains unchanged after the test, just as it was before.

How to Perform Parallel Testing

Different tools will have different approaches. We need to ensure there is a system that will enable simultaneous execution of multiple tests.

Let's see how this is done in Testsigma:

Executing Parallel Testing on Mobile Devices

For running parallel testing on mobile devices, the process must start with selecting a test automation framework. Choose a testing framework that supports parallel execution across multiple devices. Subsequently, set up and configure the test environment for parallel testing and split your test suites into smaller, independent units that can be run in parallel. The next steps often include handling dependencies and synchronization, building a comprehensive reporting and analytics process, and integrating parallel testing into your CI/CD pipeline to automate the testing process.

Testsigma, a low-code test automation tool, comes equipped with features, such as test development, test execution, reporting and analytics, and integrations for mobile testing. Checkout our detailed guide to mobile app testing to better understand the complete mobile testing process.

Automate Parallel Tests Using Testsigma

Testsigma is a robust automation testing tool that supports parallel testing. As we discussed the benefits of using Testsigma for automated testing in the previous sections, let's discuss the how-to factor. That is, how to automate parallel tests in Testsigma.

Note:You should know how to /edit/delete test plans.

There are two ways to run automated parallel tests in Testsigma,

1. You can configure tests to run in parallel while creating a new test plan.

Parallel Test Image

2. You can configure tests to run in parallel by editing an existing test plan.

Parallel Test Image

Top Parallel Testing Tools

Here are a few popular automation testing platforms that support parallel testing.

1. Testsigma

Testsigma is a robust cloud-based low-code test automation platform that allows users to automate web, mobile, and desktop apps and APIs in one place. You don't have to write any code scripts to run tests; simply create and automate tests in plain English using the NLPs.

It supports parallel testing(on the cloud as well as local devices) that lets you test your apps on various browsers, platforms, and device combos.

Testsigma makes your testing 10x faster and helps deliver your products 8x faster to the market.

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You can automate different types of testing, like,

  • UI testing
  • API testing
  • Cross-browser testing
  • Responsive testing
  • Visual testing
  • Integration testing
  • Regression testing, etc.

Top Features

  • Automate even complex workflows as plain English statements using NLPs.
  • Supports both scriptless and script-based testing. Create scriptless tests with an option to extend them in JAVA.
  • Provides record and playback feature to record user interactions and run them as automated tests later.
  • Built-in test review management feature
  • It is available as an open-source and Enterprise ready
  • Supports 3000+ real devices and tablets, and 1000+ browser/OS combos

You can avail of the open-source for free. Also, the Testsigma Cloud is available for free on a 21-day trial, where you can run automated tests on the cloud and use all the features for free.

2. Katalon

Katalon TestOps introduced parallel execution for test suites in 2021. This feature allows you to run multiple test suites simultaneously across different test environments, resulting in faster and more efficient testing.

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Katalon TestOps eliminates the need to run test suites sequentially, saving time and effort. With parallel execution, you can distribute test suites, reduce execution time, and achieve faster and more accurate results with minimal effort.

Top Features

  • A low-code test automation platform
  • Supports various third-party integrations
  • Supports web, mobile, and API testing

3. TestComplete

TestComplete by SmartBear is a test automation platform that supports parallel testing. You can run functional tests in parallel on the cloud or your local machines for continuous testing and delivery.

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Top Features

  • Automate your testing for web, mobile, and desktop apps
  • Supports scriptless testing
  • Has record and playback feature
  • Faster test execution
  • Integrate automated tests into your DevOps pipeline

4. Selenium

Selenium allows you to run multiple tests simultaneously on different environments, browsers, and devices instead of running them sequentially. TestNG, an automation testing framework, helps run tests in parallel.

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TestNG makes parallel test execution easy. You can efficiently organize tests and maintain the test case readability. You can define parallel attributes in the testing.xml file.

Top Features

  • Selenium supports multiple programming languages like PHP, Java, JavaScript, Perl, Ruby, Python, and more.
  • Supports only web application testing
  • Provides multi-browser and multi-language support
  • It is open-source and available for free
  • It is a code-based testing platform

To build and execute tests in Selenium, you will have to download prerequisites like Java, IDE, and other frameworks.

5. Kobiton

Kobiton is a cloud-based testing platform that allows you to test your mobile applications. It supports parallel testing that lets users run concurrent tests across different platforms, devices, and browser combinations.

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Top Features

Here's a short video on how to run automated parallel tests on the Testsigma Cloud,

Note - Learn more about automating parallel tests in Testsigma in the docs here.

Start automating your tests for free using Testsigma. Sign up to Testsigma Cloud and automate your tests for free in less than 2 minutes.


In today's fast-paced development environments, where time-to-market is crucial, parallel testing is a valuable approach to ensure quality without sacrificing speed.

Say goodbye to tedious, time-consuming test runs and say hello to lightning-fast, efficient testing. Start automating your tests and executing them in parallel with Testsigma and make your entire testing process faster and more efficient.