How to run tests in TestNg.xml using Maven

 Add the below code snippet inside pom.xml file

<build>
 <!-- Source directory configuration -->
       <sourceDirectory>src</sourceDirectory>
       <plugins>
           <!-- Following plugin executes the testng tests -->
           <plugin>
               <groupId>org.apache.maven.plugins</groupId>
               <artifactId>maven-surefire-plugin</artifactId>
               <version>2.19.1</version>
               <configuration>
       <!-- Suite testng xml file to consider for test execution -->
                   <suiteXmlFiles>
                       <suiteXmlFile>testng.xml</suiteXmlFile>
                   </suiteXmlFiles>
               </configuration>
           </plugin>
 <!-- Compiler plugin configures the java version to be used for compiling the code -->
           <plugin>
                <artifactId>maven-compiler-plugin</artifactId>
                <configuration>
                   <source>1.8</source>
                   <target>1.8</target>
               </configuration>
           </plugin>
       </plugins>
 </build>

Now run from project root in command prompt or terminal

>mvn clean install