public void testSetCategoryKeys() {
        // check an empty dataset
        DefaultIntervalCategoryDataset empty 
                = new DefaultIntervalCategoryDataset(new double[0][0], 
                        new double[0][0]);
        boolean pass = true;
        try {
            empty.setCategoryKeys(new String[0]);
        }
        catch (RuntimeException e) {
            pass = false;
        }
        assertTrue(pass);