/** Test method for {@link NullElement#compareTo(Element)}. */
@Test
public void testCompareTo() {
final NullElement a = new NullElement("a");
final NullElement b = new NullElement("b");
final Element other = new MaxKeyElement("a");
assertEquals(0, a.compareTo(a));
assertTrue(a.compareTo(b) < 0);
assertTrue(b.compareTo(a) > 0);
assertTrue(a.compareTo(other) < 0);
assertTrue(other.compareTo(a) > 0);
}
