    @Test
    public void testFind() {

        Integer root1 = ds.find(0);
        Integer root2 = ds.find(1);
        assertNotEquals(root1, root2);

        for (int i = 0; i < 10; i++) {
            assertEquals((i % 2) == 0 ? root1 : root2, ds.find(i));
        }
    }