@Test public void ptrbuffer04()
{

    PtrBuffer pb = make(4,5) ;
    contains(pb, 2, 4, 6, 8) ;
    pb.shiftDown(0) ;
    
    contains(pb, 4, 6, 8) ;
    pb.shiftUp(0) ;
    pb.set(0,1) ;
    contains(pb, 1, 4, 6, 8) ;
}