Over 90% of modern web apps rely on APIs, which makes API testing a key part of the development process. But as your test suites grow, running them all can take a lot of time, especially in CI/CD pipelines where quick feedback matters.
Parallel test execution helps solve this by running multiple tests simultaneously instead of one after the other. It can reduce software testing time by up to 70%, improve resource utilization, and keep release cycles moving fast without losing test quality.
How Does Parallel Testing Work?
To get a better understanding of parallel testing, let’s have a simple example of
Example 1:
API Response Validation for a Banking App
- A banking API needs to be tested for 50 different endpoints to check response time and data accuracy.
- Each test takes 1.5 minutes, meaning sequential execution would take 75 minutes.
- Running all tests in parallel completes testing in 1.5 minutes instead.
Example 2:
E-commerce Website Checkout Process
- A test checks if the checkout process works perfectly across 30 different devices and browser combinations.
- If each test takes 3 minutes, running them sequentially would take 90 minutes.
- With parallel execution, all tests can run simultaneously, reducing the total time to just 3 minutes.
When to Perform Parallel Testing?
Parallel testing should be performed when you need to test a large number of test cases or configurations across multiple environments (like different browsers, operating systems, or devices)
This is especially true when testing legacy systems, multiple versions of software, or comparing a new system to an existing one, as it allows for significantly faster execution by running tests simultaneously on various platforms.
Key Situation to Use Parallel Testing
- Cross-platform testing: When you need to test an application on different browsers, devices, and operating systems to ensure compatibility.
- Regression testing: To verify that new code changes haven’t broken existing functionality across various environments.
- Version comparison testing: When comparing the functionality of a new software version against an older version.
Best Practices for Implementing Parallel API Automation Testing
API automation testing in a parallel setup requires careful shared resource management to avoid conflicts. Parallel testing is similar to asynchronous web development in that critical differences exist.
There is no longer an assumption that tests are running in any specific order, which means that it’s essential to ensure that the environment remains untouched and that no shared resources are off-limits to particular tests.
A few of the best practices are mentioned below:
1) Test Independence
- Each test should run independently without relying on the outcome of another test.
- Avoid dependencies between tests to prevent failures due to execution order.
2) Test One Feature at a Time
- Keep tests focused on a single API function to maintain accuracy and efficiency.
- Running multiple features in one test can confuse and reduce reliability.
3) Use Scalable Test Automation Frameworks
- Choose frameworks that support parallel execution, such as vStellar test, TestNG, JUnit, RestAssured, Postman, or Katalon Studio.
- Ensure your test suite can handle multiple API requests simultaneously.
4) Reset Test Data After Execution
- Ensure that each test cleans up after itself by restoring the system to its previous state.
- Use techniques like database rollback or temporary test environments to prevent cross-test contamination.
5) Monitor and Analyze Test Results
- Implement detailed logging and reporting to track failures in parallel execution.
- Use dashboards like Allure, Extent Reports, or Grafana for real-time test monitoring.
Tools/Framework for Parallel API Test Execution
For parallel API test execution, popular frameworks/tools include:
1) vStellar Test
- vStellar Test is an advanced test automation framework designed to support parallel test execution efficiently.
- Provides built-in parallel execution for API testing, reducing test runtime significantly.
- Integrates seamlessly with CI/CD pipelines, making it ideal for continuous testing.
- Supports distributed execution, allowing tests to run across multiple environments simultaneously.
2) JUnit 5
- Supports parallel execution using annotations.
- Well-suited for Java-based API testing.
3) RestAssured
- Java-based API testing tool supporting multi-threaded execution.
- Works with TestNG & JUnit for parallel testing.
Conclusion
Parallel test execution is a powerful strategy for optimizing API testing, especially for modern web applications. Running tests simultaneously across multiple environments drastically reduces testing time, improves resource efficiency, and accelerates feedback in CI/CD pipelines.
Adopting best practices and leveraging tools like vStellar Test, JUnit 5, and RestAssured ensures seamless parallel execution. Ultimately, parallel testing enhances software quality and speeds up release cycles, making it crucial for any effective API automation testing process.
