Continuous integration and continuous delivery (CI/CD) have become integral to modern software delivery. By automating builds, tests and releases, CI/CD enables teams to ship code faster and more reliably. However, as codebases and test suites expand, sequential test execution can become a bottleneck.
This is where parallel testing comes in. By running multiple tests concurrently, parallel testing dramatically cuts down the total testing time. When integrated into CI/CD pipelines, it can accelerate releases from weeks to days or even hours.
In this post, we will dive into:
- Benefits of using parallel testing in CI/CD
- Strategies for implementing parallel testing
- Choosing the right approach for your delivery pipeline
So let‘s get started!
Benefits of Parallel Testing in CI/CD
Here are some of the major benefits of incorporating parallel testing into your CI/CD workflows:
1. Faster Test Execution
Parallel testing splits tests across multiple resources like CPUs, machines or containers. This divides the total execution time by close to the number of resources used.
A test suite that takes 5 hours sequentially, can run in 1 hour using 5 parallel executors – an 80% improvement!
2. Optimized Infrastructure Utilization
Running tests sequentially underutilizes expensive infrastructure like cloud VMs or on-premise servers. Parallel testing ensures you maximize resource usage.
Instead of 1 machine running tests for 5 hours, you can use 5 machines for 1 hour each. This saves infrastructure costs.
3. Broader Test Coverage
Time constraints often force teams to limit test scope. With faster test execution, parallel testing allows running more test cases.
Teams can expand test coverage across more platforms, browsers, devices and OS versions within the same timeframe.
4. Accelerated CI/CD Pipelines
Testing is often the longest phase in CI/CD workflows. By reducing the test duration, parallel testing directly speeds up release pipelines.
Teams can deploy code changes more frequently – from months to weeks or even multiple times a day.
Strategies for Implementing Parallel Testing
Now that we‘ve seen the benefits, let‘s explore popular techniques to enable parallel test execution in CI/CD.
Parallel Test Case Execution
This technique runs separate test cases simultaneously on multiple parallel executors. Key capabilities needed:
✅ Test isolation – Tests should not have any dependencies or shared state
✅ Test orchestration – Dynamic distribution of tests across available executors
✅ Reporting – Aggregated view of all test executions
Popular tools like Selenium Grid and testing frameworks like TestNG or JUnit provide these capabilities out-of-the-box. They allow running hundreds of UI test cases across browsers and devices in parallel.
Parallel Test Environments
Another approach is to replicate the entire test environment and run full test suites in parallel.
Modern infrastructure patterns like containers and microservice architectures facilitate building disposable parallel test environments.
✅ Spin up multiple isolated testing environments using containers
✅ Execute entire test suites in each environment
✅ Destroy environments after test completion
This approach ensures tests runs don‘t interfere with each other. Scaling up and down environments also parallelizes execution.
Hybrid Model
Organizations often use a combination of parallel test cases and parallel test environments.
Some suites like unit tests with small scope run via parallel test case execution. Bigger integration and system tests leverage the parallel environments strategy.
This hybrid model provides speed and flexibility to optimize for different types of automated checks.
Choosing the Right Parallel Testing Approach
Here are some best practices to select the best fit parallel testing strategy:
👉 Analyze test suite composition – Unit, integration, UI, security, performance etc.
👉 Study test dependency and isolation needs
👉 Review existing infrastructure and platforms
👉 Collaborate with test automation engineers on right tools and frameworks
👉 Consider ease of provisioning and managing test environments
Based on these factors, the CI/CD and test teams can derive the optimal parallel testing architecture.
You can also consider cloud testing solutions like BrowserStack. They provide ready access to thousands of real devices and browsers to run parallel tests without infrastructure overhead.
Accelerate Releases with Parallel Testing
Parallel testing techniques offer a tangible mechanism to speed up test execution. By incorporating them into CI/CD pipelines, organizations can deploy code changes faster without compromising on quality.
What approach have you taken in your projects to run automated checks in parallel? Share your experiences via comments below!
