Parallel Test Execution Using TestNG

Why Run Tests in Parallel?

As a test suite grows, running tests sequentially can take a long time. TestNG supports running tests in parallel to significantly reduce total execution time.

Configuring Parallel Execution

<suite name="Suite" parallel="methods" thread-count="4">
  ...
</suite>

The parallel attribute can be set to run tests in parallel at the method, class, or test level, while thread-count controls how many threads run simultaneously.

Things to Watch For

Parallel execution requires tests to be independent of each other (no shared mutable state), or race conditions can cause unreliable, hard-to-debug failures.