As an experienced quality assurance leader who has tested applications across thousands of mobile devices and browsers, I often get asked by software teams to define parallel testing and whether it can benefit their projects.
In this comprehensive parallel testing guide, I‘ll share exactly what it is, when to use it, and how to implement it including code examples, best practices, advantages and limitations. My goal is to provide a detailed reference for anyone looking to scale automated testing.
So let‘s get started!
Parallel Testing Clearly Explained
Parallel testing executes automated test suites simultaneously across multiple environments, operating systems, devices, and browsers. This allows for much faster feedback than standard sequential test execution.
As this diagram shows, parallel testing drastically cuts timelines by running tests concurrently:
Instead of completing tests serially one after another, parallel testing frameworks distribute tests to run in parallel. If a test suite needs to validate across 10 different platforms, parallelization could speed this up by 10x!
The associated time savings allow for more frequent test cycles, faster validation of new code changes, catching regressions quicker, and optimizing CI/CD pipelines.
Real-World Example Showing Time Savings
Let‘s look at a real-life use case to demonstrate the performance gains…
An automated UI test for a shopping cart checkout workflow takes 2 minutes per execution. Running it sequentially across 45 browser, OS, and device combinations would take 90 minutes total.
However, utilizing parallel testing tools to concurrently run 3 test executions at a time reduces the total run time down to 30 minutes – 3x faster to validate!
And for 6 parallel sessions, it drops to just 15 minutes – providing 6x time savings. The more environments that tests can dispatch to simultaneously, the bigger the return from parallelization.
When Should Teams Leverage Parallel Testing?
Here are common scenarios where utilizing parallel test execution frameworks pays major dividends:
Cross Browser & Device Testing
Running functional test suites across a matrix of real mobile devices, diverse browsers, OS versions in parallel drastically cuts validation timeframes pre-release.
New App Version Regression Testing
As updated builds introduce UI changes, integration updates, etc. – validating functionality in parallel speeds up testing cycles and release cadences.
Migrating Legacy Data to New Systems
When importing old databases or data warehouses into modernized applications, parallel data validation provides quicker feedback on any issues.
CI/CD Pipeline Acceleration
Breaking lengthy regression test suites into isolated test modules that run in parallel minimizes CI/CD bottlenecking.
Implementing Effective Parallel Testing Approaches
Now that the benefits are clear, what‘s the best way to implement parallel testing?
Start with Solid Test Architecture
First, organize test projects in a master > child relationship – allowing parallel dispatch of lower environments:
The master test suite handles coordination across the different testing matrix endpoints.
Define Entry & Exit Standards Upfront
Make sure to clearly set:
- Entry Criteria: test data loaded, environments provisioned, etc.
- Exit Criteria: pass rate thresholds defined, test module validation checks
This structures the test execution flow and reporting.
Leverage Parallel Test Runner Frameworks
Common unit testing frameworks like TestNG or MBUnit include built-in parallelization capabilities:
// TestNG Parallel Testing Example
@Test(threadPoolSize = 3, invocationCount = 10, timeOut = 1000)
public void sampleTest() {
// Testing code here
}These make it trivial to launch parallel test executions across a test matrix.
Let‘s explore both options more…
Guide to Parallel Testing with TestNG
The TestNG framework is one of the most popular open source testing tools on the market today.
It is specifically designed to handle advanced test workflows like:
- Parallel test case execution
- Parameterization for data driven testing
- Batch test case prioritization and sequencing
This section will walk through TestNG‘s parallel testing capabilities including code examples you can utilize.
Configuring TestNG for Parallelism
By adding a parallel attribute to the XML test suite definition, you inform TestNG to distribute test methods concurrently across a thread pool:
<suite name="Parallel Tests" parallel="methods" thread-count="3">
<test name="Test1">
</test>
<test name="Test2">
</test>
</suite> The thread-count value determines how many threads get spun up to run tests in parallel.
TestNG Parallel Test Execution Example
This Java + TestNG sample shows how parallel test methods speed up browser testing by dispatching tests for Chrome and Firefox simultaneously:
import org.testng.annotations.*;
public class ParallelExample {
WebDriver driver;
@Test
public void testOnChrome() {
// Performs Chrome test
}
@Test
public void testOnFirefox() {
// Performs Firefox test
}
}With the parallel config enabled, both browser test runs would execute at the same time – cutting overall execution time significantly!
Running Parallel MBUnit Tests on BrowserStack
For cross-browser testing, the BrowserStack Automate device lab provides instant access to 3000+ real mobile devices and browsers in the cloud.
MBUnit enables seamlessly executing parallel test suites leveraging BrowserStack‘s platform using these steps:
Steps for Parallel Testing with MBUnit + BrowserStack
- Configure BrowserStack credentials/parameters in the App.config file
- Build the Visual Studio solution
- Run parallel fixture tests from the Test Explorer
Including the parallel trait automatically dispatches test executions concurrently across the defined backends in BrowserStack – accelerating feedback.
The Top Advantages of Parallel Testing
Let‘s explore the major areas where adopting parallel test execution can positively impact QA teams and SDLC velocity:
Faster Test Cycle Times
By far, accelerating test execution to validate code changes faster is the #1 benefit. Running test suites in parallel slashes time to completion across multiple devices, OS, and browsers combinations.
Optimized Testing Infrastructure Costs
Using on-demand cloud testing labs optimizes usage and budgets. Rather than maintaining excess capacity or physical devices long-term, leverage virtual infrastructure only when executing tests.
Improved CI/CD Pipeline Efficiency
Lengthy end-to-end regression testing bottlenecks deployment pipelines. Introducing parallel testing breaks up test runs for faster execution – improving code flow.
This chart summarizes the difference in cycle times:
As shown, parallel test suites run significantly faster.
Limitations to Consider
However, some constraints come with a parallel approach:
Test Case Interdependencies
With parallel execution, tests cannot rely on state or side effects from other test cases. They need to act independently to avoid collisions.
Complex Application Flows
Ifvalidate application workflows have intricate sequencing or dependencies, breaking into fully independent parallel modules may be trickier.
Browser Coverage Gaps
While parallel testing greatly increases browser matrix validation, some edge case gaps may emerge compared to true distributed topologies.
Best Practices for Parallel Testing
Keep these guidelines in mind when architecting parallel testing frameworks:
Create Modular, Standalone Test Cases
Building autonomous test cases without interdependencies is crucial for parallel stability.
Isolate Testing to One Feature Area
Validating a single functionality across different configurations limits scope issues or collisions between parallel executions.
Manage Static Testing Assets Carefully
Shared static testing objects across tests executing simultaneously can cause unexpected side effects.
Reset Test Data Fully Between Runs
To prevent cross-contamination of test data between parallel test case invocations, reset state completely before and after.
Properly designing modular, independent test suites is imperative to smoothly run parallel test schedules and obtain speed + efficiency gains.
Conclusion & Summary
In closing, parallel automated testing brings faster test cycles, optimized costs, and continuous delivery acceleration. By tackling test execution bottlenecks, parallel testing allows more frequent regression testing.
This guide covered what parallel testing is, when to leverage it, implementation best practices, benefits, limitations and more. Adopting a well-architected parallel testing approach can scale test coverage and CI/CD efficiency for your team.
With on-demand access to thousands of real mobile and desktop browsers, solutions like BrowserStack enable running tests in parallel to validate releases quicker before pushing code to production.
I hope this end-to-end parallel testing reference has shed light on how teams can speed up testing! Let me know if any other testing questions come up.
