s1.add(1.0, 1.0, 1.0, 2.0);
s1.add(3.0, 3.0, 3.0, 3.0);
s1.add(2.0, 2.0, 2.0, 2.0);
assertEquals(3, s1.getItemCount());
s1.remove(new XYCoordinate(2.0, 2.0));
assertEquals(3.0, s1.getXValue(1), EPSILON);
s1.remove(new XYCoordinate(1.0, 1.0));
assertEquals(3.0, s1.getXValue(0), EPSILON);
}