What is Parallel Execution?

A closer look at parallel execution, which enables modern QA teams to speed up the testing process and improve efficiency.

A closer look at parallel execution, which enables modern QA teams to speed up the testing process and improve efficiency.

August 3, 2022
Tamas Cser

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A closer look at parallel execution, which enables modern QA teams to speed up the testing process and improve efficiency.

As software testing has evolved over time, new features and functionalities have been developed to enhance the speed, accuracy, and overall capability of the process. An integral part of this evolution is the ability to speed up the testing process, not just in speedier execution of single tests, but also in ways to run many different tests in parallel. This is the founding principle behind the concept of parallel execution in software testing.

Initially, teams would use sequential testing, where one test would only be carried out after another had ended. Based on this, the testing time could be cut down significantly if tests or groups of tests could be run simultaneously, independent of one another.

This is where the concept of parallel execution stems from and it was developed and implemented into modern testing software in order to expand functionality and efficiency.

Parallel Execution Fundamentals

In simple terms, parallel execution is a means to test multiple applications or multiple components of an application at the same time. This involves allocating testing resources to multiple branches of testing and carrying them out concurrently. In modern testing solutions, this has been taken one step further with the infusion of cloud technology, which allows for parallel execution at scale.

In modern testing solutions that support parallel execution, often with the help of a cloud infrastructure, testers can schedule groups of tests to run concurrently on separate and distinct Virtual Machines or VMs. This can involve a scenario where completely separate components of an application are running through their own testing phases with different test methods or inputs. It can also involve testing different versions of an application concurrently with the same test inputs or methods. A productive and preferred technique that involves parallel execution involves testing an application simultaneously on multiple platforms or devices, often using a simulation of different operating systems, web browsers, and display sizes.

How Parallel Execution Saves Time

If you consider an everyday testing scenario, it is quite easy to understand how implementing parallel execution can help save time during testing. For example, let us say you are planning to test an application over 12 different combinations of operating systems and browsers. If one complete test takes 5 minutes, you are looking at a total time of 60 minutes if your tests are completed in sequence, one after the other.

Pertaining to this, if you find a way to run TWO tests simultaneously on separate VMs, instead of 12 full testing intervals you just need 6, as every two successive tests can be run concurrently. This immediately cuts down your testing time by half, allowing you to complete your tests in 30 minutes. Similarly, if you find a way to run three tests concurrently, you can cut down your total testing time to 20 minutes.

Speeding up testing has been a crucial focus of testing solutions for a while. Especially in the fast-paced modern web development scenarios that can have multiple updates released daily, speed is absolutely paramount. It is in these scenarios that parallel execution can be an absolute life-saver. Choosing a testing platform that implements parallel execution efficiently can help you in many ways, including better test coverage, reducing overall testing time and therefore test debt, and bringing down overall costs.

Benefits of Parallel Execution

Adopting a testing solution that incorporates parallel execution can be justified if you learn about the many benefits of this technique. Here are a few important ones to consider.

Faster Testing

The most obvious benefit of parallel execution is faster testing. As indicated in the earlier example, being able to run tests concurrently can speed up the process of testing exponentially. Being able to test faster at scale, translates to other important benefits. One of them is the ability to find and fix bugs at the earliest opportunity.

As a consequence of parallel execution, tests are completed faster. As a result, bugs are also found exponentially faster. In fact, you do not even have to wait for the entire testing run to finish before you can start fixing the bugs already found. This means that the time taken to find and fix bugs goes down significantly, which can provide a boost to the development process. Over time, this effect compounds and affects the entire development lifecycle, allowing teams to reach new efficiency levels and ultimately reduce testing costs.

In DevOps environments, the speed of testing is often considered a critical bottleneck. The rest of the process would then have to conform to the speed of testing and not the other way around. With parallel execution, the testing can keep pace with the development process in a perfectly symbiotic relationship.

Test Coverage and Test Debt

Test coverage and test debt are contentious issues for any testing team. Moreover, when more tests can be completed in less time, this emerges as a viable solution for both these enduring problems. Therefore, parallel execution can become a vital cog in the wheel if you are looking to avoid test debt and increase test coverage.

If you can run more tests in less time, you can also run more tests overall without the extra time being that much of a liability. This helps testing teams plan for more thorough testing at the very outset, knowing they can leverage parallel execution to get through an increased number of tests faster. Especially in situations where you want to test an application on multiple combinations of browsers and platforms, parallel execution using the cloud VMs can give you a lot of leeway to work this enhanced capability into your initial testing strategy.

Similarly, this is also a profound way to avoid test debt. As your tests complete, not just on time, but before time, you can avoid test debt and adhere to your deadlines better.

CI/CD and Continuous Testing

In modern development and testing environments, the focus is often on continuous integration and continuous delivery. This workflow also requires continuous testing, using a significantly faster test cycle and more frequent testing overall. With parallel execution, you can make use of parallel tests at scale using the cloud and technologies like virtualization to get closer to your goal of achieving efficient continuous testing. This is where a testing solution with parallel execution helps you integrate your testing perfectly in the CI/CD pipeline.

This also has a cascading effect over time as it can reduce the cost of development thanks to a reliance on a cloud infrastructure for testing. Since the process is accelerated, it can also make for a faster time to market, further increasing the cost-effectiveness of the development process. For a modern DevOps testing plan, parallel execution thus becomes a critical part of the testing mechanism.

Obtaining the Full Potential of Parallel Execution

Considering these benefits and the inherent advantages of parallel execution over older, legacy test methods, it’s safe to say that you should choose a modern, capable testing solution that leverages parallel execution for a complete experience in a modern DevOps workflow.

A modern, AI-driven testing solution like Functionize can help you leverage parallel execution using the Functionize Test Cloud, which can help you run cross-browser tests at scale, including testing for different mobile platforms. This can also help you stay on top of your testing requirements with real-time performance monitoring and detailed reporting and dashboards.

This can be a poignant way to leverage the power of parallel execution and realize all of its inherent benefits for your development projects.