@Test public void set_intersection_3() 
{

    Set<Integer> x1 = set(1,2,3) ;
    Set<Integer> x2 = set(6,7,8) ;
    Set<Integer> x3 = SetUtils.intersection(x1, x2) ;
    test(x3) ;
    x3 = SetUtils.intersection(x2, x1) ;
    test(x3) ;
}