@Test
public void testEquals2() {

    assertEquals(AHashSet.empty (),
                 AHashSet.empty ());
    assertEquals(AHashSet.empty ().with("a"),
                 AHashSet.empty ().with("a"));
    assertEquals(AHashSet.empty ().with("a").with("b"),
                 AHashSet.empty ().with("b").with("a"));

    assertNotEquals(AHashSet.empty (),
                    AHashSet.empty ().with("a"));
    assertNotEquals(AHashSet.empty ().with("a"),
                    AHashSet.empty ());
    assertNotEquals(AHashSet.empty ().with("a").with("b"),
                    AHashSet.empty ().with("a").with("b").with("c"));
    assertNotEquals(AHashSet.empty ().with("a").with("b").with("c"),
                    AHashSet.empty ().with("a").with("b"));
    assertNotEquals(AHashSet.empty ().with("a").with("b").with("c"),
                    AHashSet.empty ().with("b").with("c"));

    assertNotEquals(AHashSet.empty (), null);
}