Output

d:>java -cp ".\lib\*;.\bin\;" org.testng.TestNG testng.xml
[TestNG] Running:
  D:\testng.xml

test2_1
test2_2
test2_3
test3_1
test3_2
test3_3
test1_1
test1_2
test1_3

===============================================
Suite
Total tests run: 9, Failures: 0, Skips: 0
===============================================

Test1.java

package ru.msk;

import org.testng.annotations.Test;

@Test(priority=3)
public class Test1 {

  public void test1(){
		System.out.println("test1_1");
	}
	
	public void test2(){
		System.out.println("test1_2");		
	}
	
	public void test3(){
		System.out.println("test1_3");
	}
}

Test2.java

package ru.msk;

import org.testng.annotations.Test;

@Test(priority=1)
public class Test2 {

  public void test1(){
		System.out.println("test2_1");
	}
	
	public void test2(){
		System.out.println("test2_2");		
	}
	
	public void test3(){
		System.out.println("test2_3");
	}
}

Test3.java

package ru.msk;

import org.testng.annotations.Test;

@Test(priority=2)
public class Test3 {

  public void test1(){
		System.out.println("test3_1");
	}
	
	public void test2(){
		System.out.println("test3_2");		
	}
	
	public void test3(){
		System.out.println("test3_3");
	}
}

testng.xml

<?xml version="1.0" encoding="UTF-8"?>
<!DOCTYPE suite SYSTEM "http://testng.org/testng-1.0.dtd">
<suite name="Suite">
  <parameter name="configFile" value="application.properties"></parameter>
  <test verbose="1" name="Tests" preserve-order="false">
    <classes>

     <class name="ru.msk.Test1"/>  
     <class name="ru.msk.Test2"/>  
     <class name="ru.msk.Test3"/>  

    </classes>
  </test>
</suite>