win.add(3, new Message());
win.add(4, new Message());
win.add(6, new Message());
System.out.println("win: " + win);
while((win.remove()) != null) ;
win.stable(6); // 6 is ignore as it is >= highest delivered message
System.out.println("win: " + win);
assertNotNull(win.get(2));
check(win, 0, 6, 4);
win.add(5, new Message());
check(win, 0, 6, 4);