d.add(new Year(1999), 1.0, "Series 1");
assertEquals(d.getItemCount(), 1);
assertEquals(d.getSeriesCount(), 1);
d.add(new Year(2000), 2.0, "Series 2");
d.clear();
// Make sure there's nothing left
assertEquals(0, d.getItemCount());
assertEquals(0, d.getSeriesCount());
}