Also have a look a XmlUnit (http://xmlunit.sourceforge.net/)

Write a class with name Test at the end extend TestCase.
Write methods which start with Test, and call your method from it and write assert* methods from your test method

for eg: you want to write test case for class ABC

class ABCTest extends TestCase {
public setup(){
//Anything which need to call before each of your methods.
}
public tearDown(){
//Anything which need to call after each of your methods.
}

public class testMyMethod(){
ABC abc = new ABC();
Object a = abc.mymethod();
assertNotNull("Expecting a not null object here, but not",a);
}

reply back
}