Software companies are changing how they deliver products to customers. Instead of big releases every few months, they are constantly releasing small updates, which allows them to be more responsive to customer needs.

Continuous testing is very important in this new way of delivering quality products. Testing has to happen constantly to ensure the end-to-end processes work properly. The testing teams need to collaborate closely with the development teams.

Automated testing has mostly replaced manual testing at this point. One popular automation strategy is parallel testing, which involves running multiple tests simultaneously instead of one after another. This allows for faster testing while still covering all scenarios. Parallel test execution can be done in TestNG or other automation frameworks using Selenium.

Overview of Parallel Execution

There are two main approaches to software testing: sequential testing and parallel testing. In sequential testing, different modules or functionalities of the software are tested one after the other, as well as on different browsers sequentially. While this approach is thorough, it can be extremely time-consuming.

What is TestNG?

TestNG is one of the popular automation testing tools for Java, offering robust features and benefits compared to others. It empowers users with advanced tools for efficiently designing, structuring, and running tests. With TestNG, you can access many capabilities like parallel test execution, customizable test setups, data-driven testing, comprehensive reporting, and beyond. Its versatility accommodates various test types, from unit and integration tests to end-to-end testing, making it a comprehensive solution for testing needs in web applications.

TestNG is widely embraced for several reasons:

• Flexible Test Configuration: It offers versatility in test setup through XML files or annotations. This allows for easy organization and customization of test suites, cases, and methods according to specific testing needs, streamlining test management and execution.
• Annotations and Data-Driven Testing: TestNG supports annotations like @Test, @BeforeTest, and @AfterTest, providing precise control over test execution flow. Additionally, it facilitates data-driven testing by enabling data providers to furnish test data to methods, enabling testing of various scenarios with different inputs.
• Parallel Test Execution: With built-in support for parallel test execution, TestNG permits tests to run concurrently. This capability dramatically reduces overall execution time, enhancing test efficiency. Furthermore, TestNG offers options for parallel execution at the class, method, or suite level, catering to both small and large test suites.
• Test Configuration Flexibility: TestNG provides numerous configuration options, such as test priorities, dependencies, groups, and timeouts. These features offer granular control over test execution, enabling customization of testing workflows based on specific requirements.

Parallel Test Execution in TestNG

Parallel testing can be applied to various scenarios, from testing a single application to multiple applications or even different components within an application. TestNG, a widely used testing framework for Java, offers native support for parallel test execution. It enables tests to run concurrently at different levels, such as threads, methods, and more, providing flexibility in optimizing testing efficiency.

In TestNG, parallel test execution can be achieved at different levels:

• Method level parallelism: In this approach, different test methods within the same test class are executed in parallel.
• Class-level parallelism: Here, different test classes are executed parallel, allowing for concurrent testing of different application components or modules.
• Test suite level parallelism: This approach involves running multiple test suites in parallel, enabling the parallel execution of different test scenarios or test sets.

To enable parallel test execution in TestNG, developers can use various annotations and configuration options provided by the framework. These configurations allow for specifying the level of parallelism (methods, classes, or test suites), the number of threads to be used, and other parameters to control the parallel execution behavior.

Advantages of Parallel Test Execution in TestNG

Following are some of the key advantages of parallel test execution in TestNG:

Accelerated Test Execution Speed

• Multiple tests can be executed simultaneously with parallel testing, substantially reducing overall test execution time.
• For example, if a single test takes 1 minute to complete sequentially, running five tests one after another would take 5 minutes. However, with parallel execution on five devices (or input combinations), the same five tests could be completed in 1 minute or less.

Increased Test Coverage and Wider Compatibility

• Parallel testing in TestNG allows you to test concurrently across various devices (desktop or mobile), browsers, and operating system combinations.
• This extended test coverage helps mitigate risks, reduces the chance of unnoticed bugs, and ensures wider compatibility, which is instrumental in delivering high-quality software products.

Resolve Testing Limitations

• Testing frequently emerges as a bottleneck within the DevOps pipeline, primarily due to the time-consuming nature of testing cycles, which can impede the overall release process.
• Accelerated test execution through parallel testing can help remove this bottleneck, allowing for more frequent and efficient releases.

Fix Bugs Earlier

• By completing testing earlier through parallel execution, bugs can be identified and fixed sooner in the development cycle.
• Additionally, parallel testing is results-driven, as more scenarios can be tested in less time, providing more actionable data for enhancements and improvements.

Flexibility

• Parallel testing in TestNG provides the flexibility to revert to sequential testing when necessary, allowing for a more versatile testing approach.

Cost-Effective

• Parallel testing offers a cost-effective solution by decreasing the total testing duration and potentially mitigating the requirement for extra hardware resources or testing environments.

Improved Resource Utilization

• With parallel testing, available hardware resources (e.g., machines, devices, or virtual environments) can be utilized more efficiently, as multiple tests run concurrently on different resources.

How to Implement Parallel Test Execution with Selenium and TestNG

TestNG provides several options for parallel execution, allowing you to choose the level of parallelism that best suits your test suite and dependencies. Let’s explore these options:

Parallel Execution at the Test Level

This strategy enables you to run each test suite or scenario concurrently. It’s suitable when you have independent test suites or scenarios that don’t rely on each other. You can achieve this level of parallelism by setting parallel=”tests” in the <test> tag of your TestNG XML configuration file.

<!– TestNG XML Configuration –> <test name=”Parallel Test Execution” parallel=”tests”>     <!– Test Suite 1 –>     <classes>         <class name=”com.example.TestClass1″ />     </classes>     <!– Test Suite 2 –>     <classes>         <class name=”com.example.TestClass2″ />     </classes> </test>

Parallel Execution at the Class Level

This approach allows you to run test methods within each class in parallel, with each class executing concurrently. It’s useful when you have multiple test classes, and the test methods within each class are independent. To enable this, set parallel=”classes” in the <classes> tag of your TestNG XML file.

<!– TestNG XML Configuration –> <test name=”Parallel Class Execution”>     <classes parallel=”classes”>         <!– Test Class 1 –>         <class name=”com.example.TestClass1″ />         <!– Test Class 2 –>         <class name=”com.example.TestClass2″ />     </classes> </test>

Parallel Execution at the Method Level

This strategy provides fine-grained control over parallelism by allowing individual test methods within each class to run in parallel. It’s beneficial when test methods are independent within the same test class. To achieve this, set parallel=”methods” in the <methods> tag of your TestNG XML file.

<!– TestNG XML Configuration –> <test name=”Parallel Method Execution”>     <classes>         <class name=”com.example.TestClass”>             <methods parallel=”methods”>                 <!– Test Method 1 –>                 <include name=”testMethod1″ />                 <!– Test Method 2 –>                 <include name=”testMethod2″ />             </methods>         </class>     </classes> </test>

Parallel Execution with Data Providers

TestNG supports parallel execution with data providers, which supply test data to test methods. By combining parallel execution with data providers, you can perform parallel testing with different input scenarios. To enable this, set parallel=”true” in the @DataProvider annotation.

// Test Class public class DataProviderExample {     @Test(dataProvider = “testData”)     public void testMethod(String data) {         // Test code     }     @DataProvider(name = “testData”, parallel = true)     public Object[][] testData() {         // Provide test data     } }

Best Practices for Effective Parallel Testing

Here are some best practices for effective parallel testing:

• Test Independence: Design your test scripts to be autonomous and independent of one another. Each test should be able to run independently without relying on the outcome of another test. Parallel tests must execute simultaneously so that interdependencies can cause conflicts and inconsistencies.
• Cloud Infrastructure: Parallel testing requires multiple hardware/software devices or environments for concurrent execution. Instead of investing in expensive physical devices, consider utilizing a cloud infrastructure that offers these environments as a service.

Leverage platforms like LambdaTest, an AI-powered test orchestration and execution platform that lets you run manual and automated tests at scale with over 3000+ real devices, browsers, and OS combinations.

• Avoid Static Objects: Avoid using static objects in your tests, as they can lead to conflicts when multiple tests run concurrently. One test might interfere with a static object, while another test attempts to manipulate it, resulting in unexpected behavior.
• Test Duration: Aim to design tests that have similar durations. This ensures that all tests finish around the same time, avoiding situations where most tests are completed while waiting for one slow test to finish. Consistent test lengths optimize resource utilization and minimize idle time.

Conclusion

In this blog, we explored the concept of parallel testing and outlined its benefits. Additionally, we briefly discussed how understanding TestNG can aid us in executing tests concurrently. Parallel testing helps speed up the overall testing cycle by enabling the concurrent execution of multiple test cases or scenarios, allowing projects to be delivered much faster.