public void testEquals() {

        DefaultTableXYDataset d1 = new DefaultTableXYDataset();
        DefaultTableXYDataset d2 = new DefaultTableXYDataset();
        assertTrue(d1.equals(d2));
        assertTrue(d2.equals(d1));

        d1.addSeries(createSeries1());
        assertFalse(d1.equals(d2));

        d2.addSeries(createSeries1());
        assertTrue(d1.equals(d2));