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What is TestNG?
TestNG is an open-source testing framework, where NG stands for Next Generation. It is used along with Selenium Automation as a testing tool to test web applications.
TestNG is a testing framework inspired by JUnit and NUnit which includes some new functionality that makes it more powerful and easier to use.
TestNG Vs JUnit:
TestNG and JUnit are the two most popular frameworks used along with selenium automation. Most of the features of TestNG and JUnit are similar. There are two major differences between TestNG and JUnit. The first is the Dependency Test which is not available in JUnit, and the second is Parallel Test Execution, only available in TestNG. Since we can run methods parallelly in TestNG, which is not the case in JUnit, TestNG is more preferred over JUnit.
Advantages of TestNG:
Following are some of the major advantages of TestNG.
Annotations made testers life easy.
Test cases can be grouped and prioritized more easily.
Data parameterization is possible.
Parallel test Execution which is possible with TestNG.
What is Parallel Testing?
It's a process of running test cases parallelly instead of one after another. Multiple modules can be executed together. TestNG is used with Selenium because of the importance of cross-browser testing.
Structure of Sequential and Parallel Testing:
In this section, we will see the difference with which Parallel and Sequential tests are executed.
In sequential test execution, we use a single thread to run tests, while for parallel test execution, multiple threads are generated at the start of the test execution process and then different tests are run on different threads simultaneously.
Parallel vs. Sequential Testing:
Let us see some of the differences between Parallel and Sequential testing depending upon the mode of operation, and advantages. Depending on this difference we can select which testing mode we want to use for our application.
In Parallel testing, multiple tests can be run simultaneously across different environments or configurations while in Sequential testing, tests are executed one after another.
In Parallel testing, TestNG is used to distribute test data across multiple threads, browsers, or machines. In Sequential testing, each test starts after completion of the previous test. This helps to prevent overlap of test execution.
Parallel testing significantly reduces test execution time, while Sequential testing is easy but slower than parallel testing.
Parallel testing is used in applications where high efficiency is required. Mostly, Parallel testing is used for more complex or large applications. Sequential testing is important because of the ease of operation. Mostly, Sequential testing is used for small applications.
Advantages of Parallel Testing:
Let us see some major advantages of using Parallel test execution
Reduced Execution Time:
Parallel testing reduces total test execution time by running multiple tests simultaneously. This feature of TestNG makes it specifically useful for large test execution or large-scale applications.
Allow Multi-Threaded Tests:
TestNG's parallel execution enables simultaneous running of multiple threads on test cases. This enables test execution independent of executing different software components.
Detect Issue:
Parallel testing makes it easier to find the problem faster So immediate feedback on user behavior in various situations can be provided in less time.
It also enables timely solutions which in turn reduces project time and associated costs.
Optimal Resource Utilization:
Parallel execution maximizes the utilization of system resources, such as CPU cores.
It prevents idle time, which in return provides efficient test execution.
Cross-Browser Testing:
Parallel execution allows testing across multiple browsers such as Chrome, Edge,
Firefox, etc. simultaneously. It ensures broader coverage and helps identify
browser-specific issues.
Scalability:
It supports scaling up test execution with the availability of more machines or
cloud infrastructure.
This is essential for Continuous Integration/Continuous Deployment (CI/CD) pipelines.
Faster Regression Testing:
Parallel execution accelerates regression test suites by distributing test cases
across threads or machines. This reduces delays and keeps the release cycle on track.
Disadvantages of Parallel Testing:
There are some disadvantages of using parallel test execution.
Dependent modules failed:
Parallel testing allows independent modules to run simultaneously, but in most cases, it fails when modules are interdependent. This problem arises in applications that must be completed or sacrificed for independence, in both cases more time and effort are required
Debugging Complexity:
Debugging parallel tests can be challenging due to simultaneous execution. This results in more effort and time to validate the root cause of failures or unexpected behavior.
Program flow information:
To create a balanced testing model, testers need to have a deep understanding of the application flow. Even the slightest interdependence can destroy the entire successful model. Testers need to know which modules must run simultaneously and which modules must be run separately.
Best Practices for TestNG Parallel Testing:
Implementing TestNG parallel testing effectively requires careful planning. This will not only ensure execution of tests faster, but also reliable and accurate. Some of the key best practices to follow when setting up and running parallel test cases in TestNG are:
Ensure Thread Safety:
Thread safety is one of the most critical considerations when running tests in
parallel. Since multiple threads are running simultaneously, the threads are sharing
the resources such as global variables, files, or databases.
This can lead to conflicts, which will cause data corruption or unexpected behavior.
To avoid these issues:
a) We can use synchronized methods to control access to shared resources.
b) Avoid using global variables or static fields unless they are read-only.
c) Consider using ThreadLocal variables to maintain thread-specific data, ensuring
each thread has its isolated copy.
Design Independent Test Cases:
For TestNG parallel testing to be effective, each test case should be independent
and self-contained. This means that, test cases can’t rely on the outcome or
execution of other tests.
It should avoid relying on a specific execution order by grouping or prioritizing
tests unless necessary.
Ensure each test can run in isolation without requiring setup or cleanup from other tests.
Handle Data Isolation:
Data conflicts are common in parallel testing when multiple threads access the
same data set. To prevent these issues:
a. Use separate data sets for each thread or test case to avoid conflicts.
b. Implement proper locking mechanisms to ensure data consistency using a shared
data source.
c. Utilize data providers in TestNG that support parallel execution, such as:
@DataProvider(parallel = true), to feed data into tests safely.
Optimized Thread Count:
We have used the "thread-count" attribute in TestNG to determine the number
of concurrent threads used for parallel testing. Optimizing this value is very crucial
for balancing performance and resource utilization:
We can start with a moderate thread count and gradually increase it based on
system capabilities and test complexity.
Also, we should monitor CPU, memory, and I/O utilization to ensure the system is
not burdened by too many threads.
Adjust the thread count to avoid bottlenecks like limited network bandwidth or
database connections.
Manage Resource Allocation:
When running tests in parallel, consider the availability and allocation of resources
such as network bandwidth, database connections, and external APIs:
Use connection pools to manage database connections efficiently.
Limiting the number of concurrent API calls if the external system has rate limits or
resource constraints.
Advanced Solutions to Overcome TestNG Parallel Execution Challenges:
Until now we have discussed different features, advantages, and the drawbacks of TestNG with parallel testing. Parallel execution of tests with TestNG saves a lot of execution time.
Also, due to this feature we can verify the performance of the application across different browsers. Here we can't ignore the fact that, running multiple threads in parallel results into conflicts. By using alternate solution, we can resolve the challenges occurred due to TestNG.
The HeadSpin Platform, Lambda testing are some of the examples which offers an advanced solution that addresses the common challenges of running parallel test cases. These are cloud-based environments equipped with real devices and provide advanced solutions for parallel test execution challenges, particularly for cross-browser and cross-platform testing.
These platforms ensure that our parallel testing is executed seamlessly, regardless of the scale or complexity of our test suite.
If your parallel execution needs extend to global scalability, real devices, and advanced debugging, these platforms indeed offer solutions to overcome common parallel testing challenges.