Back to Resources


Posted July 26, 2023

The Four Keys to Achieving Parallelization in Automated Testing

Leveraging parallel testing is the only way to successfully implement automated testing. But most organizations encounter hurdles as they attempt to scale their automation efforts through parallel testing. This white paper discusses the four requirements for achieving effective parallel testing.


Agile development has reached a crossroads. Most organizations have adopted modern agile development methodologies with the expectation that doing so will drive faster release cycles, improve functional quality, and lead to better customer experiences.

Yet, release velocity has stalled for many organizations. As of Q1 2023, 32 percent of organizations release software once per week to once per monththe same as reported in Q1 2021according to The State of Continuous Delivery Report 2023. Our collective efforts to deliver better software faster have hit a roadblock.

Organizations that haven't yet taken advantage of automated testing miss out on crucial opportunities to improve software release velocity.

Parallelization: The Only Path Forward

Not only that, but they must also learn to take full advantage of parallelization, which requires test automation.

At some point in their automated testing journeys, most organizations encounter the same problem: as test suites grow in volume and complexity, tests take longer to run. Testing is the foundation of agile development, so once your suites start taking too long to run, your efforts to deliver quality at speed eventually stall out.

Fortunately, there’s a straightforward solution: test parallelization. Take the hypothetical example of a suite of 100 tests, each taking two minutes to run. If you can run those tests in parallel, you’ll complete your entire suite of tests in just two minutes, enabling your developers to get the feedback they need quickly. If, on the other hand, you’re unable to leverage parallelization, that same suite of tests will take more than three hours to run, and development productivity will stall.

Leveraging parallelization is the only way to implement automated testing successfully. But most organizations immediately run into several hurdles as they attempt to scale their test automation efforts through parallel testing. Let’s examine how to overcome those hurdles by examining the four requirements for achieving effective parallel testing.

Parallelization Requirement #1: Run Atomic Tests

The most powerful and effective strategy for achieving parallelization is to run atomic tests. Atomic tests assess just one single application feature. So, rather than scripting a single test to validate that the login page loads, the username field displays, the password field displays, the logout displays, and items can be added to a cart, a team leveraging atomicity would design five separate tests that validate each of those functions individually.

Atomic tests offer many benefits. When I conduct automated testing workshops, I often open by asking attendees to guess which of the following test suites, each covering the same application features, will execute faster: a test suite featuring 18 long-flow, end-to-end tests, or a suite using 180 atomic tests. To the surprise of most, the answer is the suite featuring 180 atomic tests. In fact, when I run live demos using this exact scenario, the suite featuring 180 atomic tests typically executes 8 times faster than the suite with 18 long-flow tests!

Most organizations mistakenly assume that running longer tests in smaller quantities is a faster approach than running atomic tests in larger quantities. Thus, they attempt to combat longer-than- desired test run times by adding more validations to their tests. Doing so only adds fuel to the fire. No matter how much parallelization you apply, your test execution time will only be as fast as the slowest test in your suite. So, if you have a suite of 30 tests, 29 of which take 2 minutes to execute, and one of which takes 30 minutes to execute, you’ll have to wait the full 30 minutes to get the results of every test in that suite.

Atomicity drives stability

Automated testing suites that leverage atomic tests are far more stable than those that don’t. After all, every single validation request you add to a test is another chance for something to go wrong. Atomic tests are also far easier to debug when a test does fail. Because atomic tests execute much faster than longer tests, developers are getting feedback on code they literally just wrote, making it exponentially easier to go back and fix.

Moreover, since atomic tests focus on just one specific piece of application functionality, there’s no ambiguity about what’s broken in the event of a failed test. It can only be that one thing, and developers don’t have to waste precious time rooting around for the source of the failure. By comparison, when a non-atomic test fails, developers get no feedback on features beyond the point of the failure. So, if you’re testing 50 different elements of functionality within a single test, and the failure occurs at element 10, the remaining 40 elements go untested.

Parallelization Requirement #2: Keep Tests Autonomous

An autonomous test is one that can run completely independent of all the other tests in your suite. Many teams make the mistake of designing a multithreaded process in which one test cannot successfully execute until its predecessor has done the same.

This means, for example, that in order to execute a test validating the efficacy of your checkout function, you first have to successfully execute tests for all the functions that precede it in the application workflow. It also means that once one test fails, all the other dependent tests will fail as well. This type of co-dependent approach is a non-starter for effective parallel testing. Instead, make sure you design your tests such that they can all run entirely on their own and in any order necessary.

Parallelization Requirement #3: Correctly Manage Test Data

To implement parallel testing effectively, you must be able to control your test data. This is difficult to do even in the best of circumstances, as it depends on more than just your automation engineers to execute. But it’s especially difficult to do if you’re relying on traditional hard-coded test data, the static nature of which is a poor fit for the dynamic nature of automated testing.

Instead, the best strategy is to leverage what’s known as just-in-time data. With a just-in-time approach, you create test data, utilize it for a given automated test suite, and then destroy it at the end of the test. This cuts down on complexity and ensures that data from a previously executed test doesn’t muddy the results of your current test.

Parallelization Requirement #4: Avoid The Static Keyword

The final mandatory requirement for effective parallel testing is to avoid applying the “static” keyword to the WebDriver instance you’re managing in your test scripts. Using the “static” keyword is the fastest way to kill your parallelization dreams.

Identifying the WebDriver as “static” effectively ties the WebDriver instance to the definition of the class, not instances of the class, which means that there can only be one instance of WebDriver attached to (and shared between) all the tests in your suite. It’s like telling all the cars in the world that they have to share a single steering wheel!

Some testers will work around this roadblock by people choosing to “fork” the JVM process for each test in their suite, thus creating a new instance of the entire test suite for every test. To extend the car metaphor, this is like recognizing that your cars all share the same steering wheel and compensating for it by creating a new planet Earth for each car you want to put on the road. Not exactly the most efficient workaround. Though use of the “static” keyword is technically acceptable in certain situations, as a general rule, the best approach is to simply avoid it.

Putting It All Together: Excellence Through Automation

As you move through implementation of each of these critical requirements, it’s important to always keep the end goal in mind. That end goal, of course, is happy customers. In the modern age of digital business, the best and fastest way to turn prospects into customers (and customers into loyal advocates) is by rapidly delivering high-quality web and mobile applications. If you can achieve parallelization in automated testing, that end goal is well within reach.

Ready to scale your test automation program and release faster?

Let's talk

© 2023 Sauce Labs Inc., all rights reserved. SAUCE and SAUCE LABS are registered trademarks owned by Sauce Labs Inc. in the United States, EU, and may be registered in other jurisdictions.