@Test public void ptrbuffer05()
{

    PtrBuffer pb = make(4,5) ;
    contains(pb, 2, 4, 6, 8) ;
    pb.shiftUp(2) ;
    pb.set(2, 0) ;
    contains(pb, 2, 4, 0, 6, 8) ;
    pb.shiftDown(2) ;
    contains(pb, 2, 4, 6, 8) ;
}