TestNG is bundled with there IntelliJ installation. In-case if its disabled in the IDE, we can enable the plugin using the below steps.

Steps to Enable

File >> Settings… >> Plugins

Click on the Installed tab.

Search for TestNG plugin.

Adding TestNG to project

We can add the TestNG dependency to the Maven project. Its a one time step to configure the TestNG in the project.

Just add @Test annotation, click on the red bulb icon and click on the drop down.

Choose Add Maven dependency…

<dependencies>
        <dependency>
            <groupId>org.testng</groupId>
            <artifactId>testng</artifactId>
            <version>7.1.0</version>
            <scope>test</scope>
        </dependency>
</dependencies>

Maven would automatically download the latest TestNG jar artifact to the local repository ( .m2 directory).