Add TestNG to gephi-parent

pom.xml

@@ -725,6 +725,16 @@
             </dependency>
         </dependencies>
     </dependencyManagement>
+    
+    <!-- TestNG dependency -->
+    <dependencies>
+        <dependency>
+            <groupId>org.testng</groupId>
+            <artifactId>testng</artifactId>
+            <version>6.8.7</version>
+            <scope>test</scope>
+        </dependency>
+    </dependencies>
 
     <build>