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February 15, 2023

The Essential Guide to Parallel Testing

Continuous Testing

In the age of digital transformation, test automation is more critical than ever. But whether you are getting started or looking to scale your testing efforts, you may find that even when automated, your testing can take too long to match up to your organization's sprint schedule. 

To address this challenge, many teams adopt parallel testing as part of their overall testing strategy. This technique helps teams reduce their overall testing time while also expanding their test coverage and reducing overall costs. 

Sound too good to be true? 

This blog will take a closer look at parallel testing and share the benefits that it provides testing teams. We will also clue you in to some common challenges you may run into as you get started.

Feel free to read along or jump to the section that interests you most. 

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What Is Parallel Testing?

Parallel testing is the practice of executing multiple tests concurrently to reduce overall test execution time for various application components. Parallel tests feature more than one test or system check being executed simultaneously on different devices and browser configurations.

The opposite of parallel testing is sequential testing. This entails executing one test after another. This is a much more time-consuming approach to testing.

Related Reading: How to Do Cypress Parallel Testing >>

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How Does Parallel Testing Work?

In parallel testing, a tester runs two or more versions of software concurrently with the same input or test methods. Alternately, a single version of the software can be run simultaneously across multiple devices or desktop OS/browser combinations.

By integrating test automation frameworks with a cloud-based solution, which takes care of device management, you can easily scale automated test across platforms in parallel.

Related Reading: Choose Your Devices for Parallel Testing With Perfecto's Test Coverage Guide 

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4 Benefits of Parallel Testing

The main benefit of parallel testing is that it accelerates execution across multiple versions. Here are a few more benefits to consider.

1. Accelerate Execution

From a speed to execution perspective, consider this. If a singular test takes one minute to execute and you run 10 tests synchronously, the total time to execute all tests takes 10 minutes.

However, if you run that same test that takes one minute across 10 parallel devices, the total test time takes just one minute. This can provide major time savings when testing at scale.

2. Increase Test Coverage

Improved test coverage is another benefit of parallel testing. It allows you to test across more mobile devices or desktop OS/browser combinations at once. Extended test coverage mitigates risk and reduces the chance of releasing with escaped defects.

Related Reading: 5 Things to Consider When We Talk About Test Coverage

3. Break Through the Testing Bottleneck

All too often, testing is the bottleneck of DevOps. Tedious testing holds up the entire cycle. But parallel testing helps you remove the bottleneck, accelerating testing and significantly reducing the risk of on-going quality visibility.

4. Fix Bugs Earlier

Parallel testing also allows for bug fixes during the sprint rather that after. This significantly reduces developers’ bug fixing time and gives them more time to innovate and create new features, rather than just continually fixing bugs.

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Overcome Parallel Testing Challenges

As with any type of testing, you may run into some difficulties in achieving full-blown parallel testing.

A common challenge that teams face has to do with scalability and the availability of a secure, enterprise-grade lab that meets their requirements.

While DIY testing labs are typically considered, managing and maintaining an in-house lab is difficult and costly. It’s much more difficult to scale an in-house lab. Plus, scaling requires a significant IT investment.

An always-on, always available fully-managed lab with commonly available devices and instances of OS/browser combinations is a requirement for conducting parallel testing successfully.

A lab like Perfecto’s test cloud has all the platforms you need to test against, so scaling with parallel testing is easy. Plus, you can apply real user conditions for more accurate testing.

Related Reading: Cloud Testing Is More Critical Than Ever

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Parallel Testing Example

Teams can perform parallel testing with a variety of testing frameworks, such as Selenium, Playwright, and Appium. By integrating Perfecto with these and many other testing frameworks, teams can speed up their executions by testing in parallel all in one intuitive platform. 

The following example will showcase how to do parallel testing with Perfecto and Cypress, a popular web testing framework.

Cypress Parallel Testing Example

Cypress parallel testing


After installing the Cypress SDK, you will need to install the Perfecto-config.json file and define the different platforms that need setting up. When you run the command perfecto-cypress-run with the config.json, you can see all of the spec.js files that you can either test on Cypress’s demo website or within the Perfecto cloud.

To run these Cypress parallel tests on the Perfecto cloud, you must upload and configure the spec.js files as a zip file to the demo cloud. After each execution, you can also see within the Perfecto platform all the test reports with the Cypress logs, visuals, recordings, and other configurations that are coming with the test cases themselves. 

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Parallel Testing Best Practices

Ensure that you are making the most of your parallel testing efforts with these best practices:

  • Choose your tests wisely. While parallel testing is certainly helpful, it does not apply to all types of tests. For example, inter-dependent tests will not run well in parallel, since they need another test to finish executing before they can run. In addition, it is important to consider any infrastructure limitations that you might have in order to prevent false negatives that come from a lack of necessary resources.

  • Keep tests autonomous and atomic. Parallel tests should only test one specific thing at a time, and not be dependent on another script running successfully beforehand. Sticking to these two guidelines make the task of managing your parallel tests easier. 

  • Keep tests a similar length. By keeping your scripts the same length, you can also ensure that each parallel test takes the same amount of time to run. This strategy helps keep parallel testing more efficient.  

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Bottom Line

Parallel testing is a critical component to any DevOps testing strategy.

It can help you tackle the mountain of permutations to test in a timely manner. By saving you time, and thus reducing costs, parallel testing is a valuable addition to your testing.

Perfecto can help your team achieve parallel testing in the cloud. With Perfecto, you can:

  •  Test against devices and browsers in the cloud.
  • Debug easily without recreating the test environment.
  • Scale testing across platforms.
  • Increase visibility with test reporting and analytics.
  • Integrate with anything in your toolchain.

Try parallel testing your web and mobile apps with Perfecto. Start your free 14-day trial today.

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This blog was originally written in March 2020, but has since been updated for content and clarity. 

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