TestNG Documentation

What it is

TestNG is an open source testing framework for Java, inspired by JUnit and NUnit. It is used for unit tests, but it is especially common in Selenium test automation projects, where its data providers, groups and parallel settings are useful for browser suites.

What the documentation covers

• Annotations: @Test, @BeforeMethod, @AfterMethod, @BeforeClass, @BeforeSuite and the rest of the lifecycle, which is where a Selenium suite creates and quits its driver.
• Data providers: @DataProvider methods that feed rows of data into one test, the natural way to automate the partitions and boundaries you designed by hand.
• Groups and dependencies: tagging tests as smoke or regression and choosing which to run.
• Parallel execution: running methods, classes or tests in parallel threads, with thread-count settings.
• testng.xml: suite files that define which classes, groups and parameters to run without recompiling.
• Listeners and reporters: hooks for taking screenshots on failure and producing reports.

Is it worth your time?

If you are joining a Java Selenium team, very likely yes: many existing suites use TestNG, and understanding annotations, data providers and parallel settings is part of daily work. If your team uses JUnit 5 instead, the concepts transfer directly. The documentation is a single long page rather than a course, so use it as a reference alongside building a real project.

Prerequisites

Basic Java, including classes and methods, and a build tool such as Maven or Gradle to add TestNG as a dependency. Current TestNG versions need JDK 11 or newer, according to the official page.

Free or paid?

Free and open source under the Apache 2.0 licence.

What you can do after

Structure a Selenium suite with clean set-up and teardown, drive tests from data, split smoke and regression groups, run tests in parallel against a Grid and capture evidence through listeners.

Common questions

TestNG or JUnit 5? Both are solid. TestNG remains very common in Selenium projects; JUnit 5 is the default in many modern Java codebases. Learn one well and recognise the other.

Why do my parallel tests interfere with each other? Usually a static, shared WebDriver. Create one driver per test method or per thread.