What is Parallel Testing? An Introduction to Parallel Testing

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June 04, 2026 · 9 min read · Testing Guide

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Posted April 13, 2023

What is Parallel Testing? An Introduction to Parallel Testing

Learn why parallel examination is a powerful tool for development squad to have in their automated examination strategy.

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What could be better than using test automation software to formalise applications quickly and efficiently? Running those tests at the like time via parallel examine! Parallel screen dramatically reduces testing clip, get more efficient use of resources, and gets your features to grocery faster.

That said, there are some significant caveat to keep in mind to get the most of parallel testing, as well as some pit that you may have to work around to avoid interrupt parallel trial workflows.

Keep reading for tips on how parallel testing deeds, why it & # x27; s beneficial, when to use it, and which best practices help to make parallel tests as effective as possible.

What is Parallel Testing?

Test parallelization is the pattern of executing multiple software exam simultaneously. It & # x27; s the opposite of serial examination, which requires one test to finish before starting another.

Shorten Test Run Time

The most common use case for parallel examination is in the performance of a entourage of functional tests. Imagine if you had a suite of 120 Selenium trial, which takes an average of 2 minutes per tryout to complete. Running serially on one browser or mobile gimmick, this cortege would conduct 4 hours (120 tests x 2 minutes = 240 minutes) to run.

Now imagine bunk this rooms in parallel, with enough compute ability to run all tests at the same time.

It would take 2 proceedings.

To run the example, imagine that you needed to run this test on Chrome, Edge, Safari, Firefox, Safari-mobile AND Android-Chrome. If you had enough compute powerfulness, you could still run the entire suite in 2 bit.

If you only had plenty compute power to run on one platform at a time, it would occupy 12 min (2 second for 6 different platform). If you only had decent powerfulness to run half of the tests at a clip, it would merely guide two-bagger that, which is still a far vision faster than running serially.

No matter how you crunch the number, you can get far more reportage in far less clip by running exam in analogue.

What Are the Advantages of Parallel Testing?

The welfare of parallel prove include:

Broader test coverage in the same period: By executing many examination simultaneously, you can perform more tryout in the same quantity of time. That means you can examine across more devices, operating system, and browser conformation to acquire great confidence that your app works as need.
Less testing time: Parallel testing can trim the entire clip required to perform tests. For model, if you have ten examination that each takes two transactions to dispatch, bunk them in parallel lets you dispatch the entire test routine in two minutes. With serial examination, you & # x27; d be look 20 minutes for those tests to finish.
Resource efficiency: Parallel testing helps make the most efficient use possible of uncommitted testing imagination. Each individual test requires a small amount of CPU/memory, leave a lot of wild resources. With parallel examination, you can run as many simultaneous tests as your infrastructure can handle. This is a particularly significant vantage if you & # x27; re paying for approach to test infrastructure by the min and need to optimise resource efficiency to save money.

In little, parallel testing is a great way to run more tests, in less time, with more effective use of resource, and at a low toll.

How Does Parallel Testing Work?

Although you could theoretically run parallel tests manually if you had multiple people perform each manual tryout at the same time, parallel testing usually relies on to execute multiple tests automatically and simultaneously.

You can execute parallel testing use any test automation framework that supports it, using whatever language uncommitted.

For autonomous testing across multiple user personas, check out SUSATest — it explores your app like 10 different real users.

To set up parallel tryout, perform these steps:

Decide which tests you will run in parallel. As noted below, some tests shouldn & # x27; t or can & # x27; t run in analogue, so you need to determine which exam are a good fit.
Write the examination. Write code to automatise each test to be run in analog.
Schedule tests: Some test mechanisation fabric provide built-in scheduler that you can use for this purpose, or you could use an external scripting tool to trigger tests free-base on a schedule.
Execute the tests. Let the tests run, being sure to monitor them to ensure that they all execute as take.
Examine test results. If any tests neglect, determine why, and compare issue from multiple tests to assess whether the issue that triggered the failure affect multiple form or are specific to one device, function system, or browser.

You believably don & # x27; t need any special tools to run tests in parallel. If you & # x27; re already employ automated testing, become your automated tests into parallel tests does not require extensive work. The lonesome variable is the framework and platform you & # x27; re using -- some support parallelization best than others, and some program aren & # x27; t conducive to parallel examination.

Some platforms (iOS simulator, for example) alone allow you to run a single parallel thread per calculator, which would command multiple separate machines to be set up. This is why a cloud solution might be best -- they set up the environment, and all you involve to do is send over the trial!

Parallel testing examples

As instance of tests that are good candidates to run in parallel, consider the following tests written for different frameworks.

Selenium parallel testing example

This tryout is a good fit for test parallelization because it has no data habituation and could be executed across multiple control systems simultaneously:

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signification org.openqa.selenium.WebDriver;
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import org.openqa.selenium.firefox.FirefoxDriver;
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importation org.openqa.selenium.support.PageFactory;
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import org.testng.annotations.Test;
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public class SeleniumTest {
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    @Test
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public void testSelenium () {
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// Create a new example of the Firefox driver
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WebDriver driver = new FirefoxDriver ();
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// Navigate to the Google home page
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driver.get (& quot; http: //www.google.com & quot;);
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// Instantiate a new Page Object and populate it with the driver
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GoogleHomePage page = PageFactory.initElements (driver, GoogleHomePage.class);
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// Perform a search on the page
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page.searchFor (& quot; Selenium & quot;);
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    }
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}

Appium parallel prove example

Here & # x27; s a similar test you could run in across multiple device case at the like time:

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signification org.junit.Test;
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signification org.openqa.selenium.By;
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import org.openqa.selenium.WebDriver;
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import org.openqa.selenium.WebElement;
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import org.openqa.selenium.remote.DesiredCapabilities;
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import org.openqa.selenium.remote.RemoteWebDriver;
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public grade AppiumTest {
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@Test
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public void tryout () shed MalformedURLException {
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// Set the Desired Capabilities
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DesiredCapabilities caps = new DesiredCapabilities ();
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caps.setCapability (& quot; deviceName & quot;, & quot; My Device & quot;);
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caps.setCapability (& quot; platformName & quot;, & quot; Android & quot;);
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caps.setCapability (& quot; platformVersion & quot;, & quot; 9.0 & quot;);
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caps.setCapability (& quot; appPackage & quot;, & quot; com.example.android.myApp & quot;);
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caps.setCapability (& quot; appActivity & quot;, & quot; com.example.android.myApp.MainActivity & quot;);
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// Instantiate Appium Driver
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WebDriver driver

Playwright parallel try instance

And in, here & # x27; s a test that could run across different operating systems:

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const{ chromium }=require(& # x27; playwright & # x27;);
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(async()=>{
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const browser =await chromium.launch({headless:false});
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const page =await browser.newPage();
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await page.goto(& # x27; https: //www.google.com & # x27;);
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// Type into search box.
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await page.type(& # x27; # search input & # x27;,& # x27; Hello World & # x27;);
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// Click hunt button.
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await page.click(& # x27; input [type= & quot; submit & quot;] & # x27;);
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})();

Challenges and Limitations of Parallel Testing

While parallel examine can speed and optimise prove in many cases, it has its limitations. Parallel testing may not work for tests where the next challenge will make issues for efficient test execution:

Inter-dependent examination: If you have a test that requires another test to be complete before the test can run, you won & # x27; t be able to run the tests in latitude. This limitation applies virtually often in situations where you don & # x27; t need to start one test if a previous test results in a failed state, in which case something is incorrect and you desire to deflect wasting time and resources running additional tests until you fix the issue that triggered the failure in the one test.
Data dependencies: If multiple tests require access to the same data, such as an entry in a database, running the tests in parallel can be difficult or impossible because each tryout will be trying to fetch or alter the same data at the like clip. Parallel tests should not have data dependencies.
Infrastructure limitations: If your infrastructure is capable of supporting entirely a limited number of tests at one clip, you & # x27; ll receive to limit examination parallelization. Attempting to run more coinciding tests than your infrastructure can handle can result in tests that fail -- probably inconsistently -- due to a lack of available resources.

Best Practices for Parallel Testing

To make the most of parallel testing, adhere to these key principles:

Write : Atomic tryout are tests that evaluate one specific thing rather than trying to test many thing at erst. Managing parallel tests – and avoiding situation where tests contend for resources – is leisurely when each test is nuclear.
Write autonomous tests: An sovereign test is a examination that can run at any time without depending on early exam.
Keep tests like in length: To do the most of parallel testing, design each test so that it will take approximately the same amount of entire clip to run. Otherwise, you could end up with a quiz procedure where most of your tests have finished, but you are still wait on one of them, which is inefficient.
Be strategical about which tests to run: Even with parallel testing, there are limits on how many tests you can run at once, so you & # x27; ll need to be calculated about what you test for and which configurations or environments you test on. In former language, don & # x27; t treat parallel prove as a license to run infinite tests.

Run Parallel Tests on Sauce Labs

With support for, the Sauce DevOps Test Toolchain makes it leisurely to run parallel trial whenever and however you want. Take advantage of the to access test infrastructure on demand, and take advantage of tools for monitoring tests and troubleshooting failure across any test within your examination parallelization suite.