In this tutorial, we will understand below topics –
– What is TestNG?
– TestNG Maven
– How to configure TestNG in Eclipse?
– TestNG Plugin Configuration in Eclipse
https://www.onlyfullstack.com/what-is-testng-how-to-configure-testng-in-eclipse/

Part 2 – TestNG Annotations

– Annotations in TestNG
https://www.onlyfullstack.com/testng-annotations/

Part 3 – How To Run Multiple Test Suites In TestNG With Surefire Plugin?

– What is TestNG Suite?
– How to write testng-suite.xml
– How to configure the SureFire Plugin with TestNG?
https://www.onlyfullstack.com/how-to-run-test-suite-in-testng-with-surefire-plugin/

Part 4 – Testng Groups Test

– What is TestNG Group?
– How to specify and run the TestNG group?
https://www.onlyfullstack.com/testng-groups-test/

Source Code
You can find the complete source code on below GitHub repository – 
https://github.com/onlyfullstack/testng-tutorial