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What Is Parallel Testing?
Everything You Wanted to Know

Posted On: 17 January 2023

With DevOps, Agile, and Lean going strong, the application deliveries appear to be fundamentally different from a few years ago. Developers are more efficient, release cycles are faster, and there are no layers of bureaucracy.

Yet, the testing world finds itself amidst a constant barrage of bugs and product defects. So, where’s the disconnect? And how to fix that?

This article unearths these challenges and presents parallel testing as a unique solution. It can help put testing back to its rightful place as a strategic partner in delivering quality software consistently and reliably.

What is Parallel Testing?

Parallel testing involves testing multiple application components across different systems at the same time. This approach speeds up test cycles, maximizes test coverage, and avoids common pitfalls of sequential testing.

For this reason, parallel testing supports a variety of use cases. For example, it serves well when determining if the new system performs well as compared to the existing system. This is checked by running both the systems for some time and comparing the outputs from both of them.

Likewise, it helps execute the same test cases on multiple environments simultaneously to ensure consistent results — this is especially viable for testing an application or its component across different browsers, devices, etc. This way, the test execution time is significantly reduced, allowing the development team to shorten the time-to-market.

As soon as the code is built, parallel testing executes the tests in tandem across multiple platforms. As a result, any issue can be proactively fixed for a successful build. This process repeats until the product is stable enough for release.

How does Parallel Testing Nullify the Testing Challenge?

The sequential style of software testing limits the testing to one iteration at a time, making it a slow process. This is especially true for performance testing, where the tester needs to run multiple test cases within a small-time window. There’s also a high level of dependency within an iteration because sequential software testing requires the outcome of one test to inform subsequent tests.

On the other hand, parallel testing enables testers to run multiple test casessimultaneously. This is very beneficial when changing from legacy software to modern applications. Testers can concurrently test the new software against reference environments (both old and new) to carve out the differences between the output. Such a process saves time and resources while ensuring the stability and success of the product.

How is Parallel Testing Beneficial?

Parallel testing helps identify the root cause of anomalies faster. But, how does this help the business case?

Benefits of parallel testing-ACCELQ

Advocates for broader test scope:

Customarily, teams test any release against a set of configurations and environments. These environments predominantly pertain to the most popular browsers and devices, and understandably so. But, often, it is important to also verify against other variations of the same. For example, if a product is developed on Windows or macOS, it is helpful to test on the equivalent in a Linux environment. Doing so would allow any bugs to surface earlier and quicker and provide opportunities to scale further down the line.

Consumes a fraction of the usual testing time:

The reduction in the time for testing is directly proportional to the number of test cases being concurrently run. And the number of test cases run is a function of the sophistication of the application under consideration. In other words, as the testing scope increases and the segregation of the test cases proliferates, QA teams can test more devices and configurations. This means that the testing time will decrease relative to the test case execution.

Parallel Tests make repetition a boon:

Since the test cycle rapidly iterates and the number of test cases increases, the developer can build a comprehensive regression suite at each release. In turn, this helps increase the chances of identifying abnormal occurrences more frequently and producing more decision-centric data.

Consumes a fraction of the usual testing cost:

Test automation and cloud setup make it possible to reduce the financial and personnel resource expenses. Also ensuring that the product or service stays up-to-date and remains competitive. This will be critical in the forthcoming years when there will be greater demand for modern and scalable products.

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Complements the existing testing philosophy:

It is essential to understand that parallel testing works as a supplement to the traditional testing pipeline. Indeed, parallel testing is a better way of doing things; however, it doesn’t necessarily entail tweaking the built-in sequences of the existing software testing process. It is up to the tester to decide whether they want to achieve their organizational value sequentially or in parallel.

Considerations Before Making a Switch to Parallel Testing

Now that we understand the Parallel testing definition, it is also necessary to understand that Parallel testing can be a powerful tool in making iterations more efficient to the point of making them more effective. However, there are some prerequisites to address:

Considerations of parallel testing-ACCELQ

Comprehensive product knowledge is imperative

Familiarity with the product is critical to testing it in parallel. It requires the tester to be highly focused on the product and the rationale behind its development. For example, the interface and design principles. The tester must also be knowledgeable about the specifications for each iteration and the timescales for which a release is allowed to be finalized.

Awareness of the data dependencies

Some tests may rely on different sets of data to test a specific property or function. As long as the tester knows what data to provide for a test, how to get it, and how to mix and match with other data sets provided by other tests, they can proceed with parallel testing.


Parallel Testing broadens the scope and relevance of tests and reduces testing time and cost. It makes it essential that software testers are more familiar with the application under test and can come up with a testing approach that complements the existing testing framework.



Director, Product Evangelist at ACCELQ.


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