testng-parallel

Enable parallel execution in testng.xml by setting the parallel attribute (suite, class, method, or instance) and configuring thread-count to control how many threads execute tests concurrently. This distributes test load across threads to maximize throughput while maintaining isolation.

Use ThreadLocal storage to isolate resources per thread and synchronize access to shared resources. These patterns prevent data corruption and race conditions when multiple test threads access the same objects or external services simultaneously.

Yes, TestNG supports data-provider concurrency alongside suite, class, and method parallelism. Configure thread-count and parallel settings in testng.xml to execute data-provider iterations concurrently while maintaining thread safety for shared resources.

Set parallel mode to class or method and configure thread-count to match your environment count. Use ThreadLocal storage to assign each thread its own browser instance or service connection, ensuring resource isolation across parallel test execution.

TestNG offers suite (all tests in parallel), class (tests within classes in parallel), method (individual test methods in parallel), and instance (test instances in parallel). Choose based on your test structure: method offers finest granularity, suite offers coarsest.

Parallel execution is configured in testng.xml, not code. However, ensure your tests are thread-safe by avoiding shared mutable state and using ThreadLocal for per-thread resources. Existing thread-safe tests typically require no code changes.