public void testAdd() {
        XIntervalSeries series = new XIntervalSeries("Series", false, true);
        series.add(5.0, 5.50, 5.50, 5.50);
        series.add(5.1, 5.51, 5.51, 5.51);
        series.add(6.0, 6.6, 6.6, 6.6);
        series.add(3.0, 3.3, 3.3, 3.3);
        series.add(4.0, 4.4, 4.4, 4.4);
        series.add(2.0, 2.2, 2.2, 2.2);
        series.add(1.0, 1.1, 1.1, 1.1);
        assertEquals(5.5, series.getYValue(0), EPSILON);
        assertEquals(5.51, series.getYValue(1), EPSILON);
        assertEquals(6.6, series.getYValue(2), EPSILON);
        assertEquals(3.3, series.getYValue(3), EPSILON);
        assertEquals(4.4, series.getYValue(4), EPSILON);
        assertEquals(2.2, series.getYValue(5), EPSILON);
        assertEquals(1.1, series.getYValue(6), EPSILON);