TestNG is an open-source next-generation automated testing framework developed to eliminate the inadequacies in Junit. This automated test framework comes with new functionalities and systematic approaches to make it easier for software testers and developers to perform automated testing. Here's what makes the TestNG framework one of the best testing automation frameworks.

Advantages of TestNG Framework

TestNG is preferred by developers for its ability to write powerful test cases with the help of annotations, grouping, and parametrizing. It covers all classifications of test automation like Unit testing, Functional testing, End-to-End, and integration testing. It's available in the form of jar files. TestNG has multiple class interfaces and methods which will make tester tasks easy. TestNG provides additional functionality to create a robust framework.

• Annotations are easy to understand
• Easy to group test cases
• Parallel testing is possible
• Supports parameterized and dependency tests
• HTML Reports are generated by default

Using TestNG in Selenium

By default, the Selenium testing process does not produce an appropriate format for the test result, for this reason, most Selenium users use TestNG. The following are some other features that prompt Selenium users to use TestNG.

• Numerous test cases can be organized with ease by translating them into the testng.xml file
• Sets priorities on test case execution 
• A test case can be executed at different times using the keyword invocationCount by assigning an iteration number to invocationCount variable
• Supports cross-browser testing and supports tools like Maven, Jenkins etc.
• Unlike WebDriver, TestNG has a built-in mechanism to generate reports in a readable format
• Comprised of default JDK functions for runtime and logging

Steps to Install TestNG in Eclipse

Step 1: Launch eclipseIDE ->click on help option -> eclipse-> marketplace option
Step 2: Enter the keyword “TestNG “in the search box and then click "go"
Step 3: Click "install" 
Step 4: A confirmation window will open, click "confirm" 
Step 5: The application will prompt you to accept the license and then click "finish" 

Annotations of TestNG

Annotations help deliver additional information regarding the program. It starts with ‘@’. It doesn't modify the action of a compiled program and helps associate metadata to the program elements (i.e. instance variables, constructors, methods, classes, etc).

List of TestNG Annotations

• Before Suite: Runs before the execution of all the test methods 
• After Suite: Runs after the execution of all the test methods
• Before Test: Executed before all the test methods of available classes 
• After Test: Executed after all test methods of available classes 
• Before Class: Executed before the first method of the current class is invoked
• After Class: Invoked after the execution of all test methods of the current class
• Before Method: Executed before each test method runs
• After Method: Runs after the execution of each test method
• Before Groups: Runs only once for a group before the execution of all test cases belonging to that group
• After Groups: Runs only once for a group after the execution of all test cases belonging to that group

Conclusion

TestNG makes automated tests more organized, readable, maintainable, effective, and user-friendly. Its high-end annotations make it simple to scale while executing cross-browser testing across multiple devices, browsers, and their versions.