public void testEquals() {
        XYSeries s1 = new XYSeries("Series");
        s1.add(1.0, 1.1);
        XYSeriesCollection c1 = new XYSeriesCollection();
        c1.addSeries(s1);
        XYSeries s2 = new XYSeries("Series");
        s2.add(1.0, 1.1);
        XYSeriesCollection c2 = new XYSeriesCollection();
        c2.addSeries(s2);
        assertTrue(c1.equals(c2));
        assertTrue(c2.equals(c1));

        c1.addSeries(new XYSeries("Empty Series"));
        assertFalse(c1.equals(c2));

        c2.addSeries(new XYSeries("Empty Series"));
        assertTrue(c1.equals(c2));