((Factory)this).setCallback(0, new MethodInterceptor() {
Enhancer.registerCallbacks(getClass(), new Callback[]{new MethodInterceptor() {
    public void test() {        assertTrue(foo() == 0);        ((Factory)this).setCallback(0, new MethodInterceptor() {            public Object intercept(Object obj, java.lang.reflect.Method method, Object[] args, MethodProxy proxy) {                return new Integer(1);            }        });        assertTrue(foo() == 1);    }