@Test public void ptrbuffer07()
{

    PtrBuffer pb = make(4,5) ;
    contains(pb, 2, 4, 6, 8) ;
    pb.shiftUp(3) ;
    pb.set(3, 1) ;
    contains(pb, 2, 4, 6, 1, 8) ;
    pb.shiftDown(3) ;
    contains(pb, 2, 4, 6, 8) ;
}