s1.add(1.0, 1.1, 1.2, 1.3);
c1.addSeries(s1);
assertFalse(c1.equals(c2));
XIntervalSeries s2 = new XIntervalSeries("Series");
s2.add(1.0, 1.1, 1.2, 1.3);
c2.addSeries(s2);
assertTrue(c1.equals(c2));
// add an empty series
c1.addSeries(new XIntervalSeries("Empty Series"));
assertFalse(c1.equals(c2));