Multiple Before and After annotation options: TestNG provides multiple kinds of Before/After annotations for support of different setup and cleanup options.

XML-based test configuration and test suite definition: Test suites in TestNG are configured mainly using XML files. An XML file can be used to create suites using classes, test methods, and packages, as well as by using TestNG groups. This file is also used to pass parameters to test methods or classes.

Dependent methods: This is one of the major features of TestNG where you can tell TestNG to execute a dependent test method to run after a given test method. You can also configure whether the dependent test method has to be executed or not in case the earlier test method fails.

Groups/group of groups: Using this feature you can assign certain test methods into particular named groups and tell TestNG to include or exclude a particular group in a test.

Dependent groups: Like dependent methods, this feature allows test methods belonging to one group being dependent upon another group.

Parameterization of test methods: This feature helps users to pass parameter values through an XML configuration file to the test methods, which can then be used inside the tests.

Data-driven testing: TestNG allows users to do data-driven testing of test methods using this feature. The same test method gets executed multiple times based on the data.

Multithreaded execution: This allows execution of test cases in a multithreaded environment. This feature can be used for parallel test execution to reduce execution time or to test a multithreaded test scenario.

Better reporting: TestNG internally generates an XML and HTML report by default for its test execution. You can also add custom reports to the framework if required.

Open API: TestNG provides easy extension of API, this helps in adding custom extensions or plugins to the framework depending upon the requirement.