A Guide to Parallel Test Execution in API Automation Testing

Parallel testing is a testing methodology in which multiple test cases are executed simultaneously. This approach provides faster feedback, allows for early detection of issues, and optimizes the use of computing resources. It is especially beneficial in larger projects, where executing test suites sequentially can be time-consuming.

During parallel testing, a tester runs two separate versions of the software concurrently using the same input. This testing can be performed either manually or with the help of test automation tools and frameworks.

One of the studies evaluates the impact of parallelization on feedback time in continuous integration, introducing novel approaches to optimizing test execution.

What Is Parallel Testing?

Parallel testing is the process of utilizing automation testing capabilities by allowing the execution of the same test in multiple environments simultaneously.

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 device and browser combinations.
• If each test takes 3 minutes, running them sequentially would take 90 minutes.
• With parallel execution, all tests can run at the same time, 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 quickly 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 management of shared resources 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 important to ensure that the environment remains untouched and that no shared resources are off-limits to specific 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 cause confusion 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 framework/tools and frameworks 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.