@Test public void other() throws Exception {

    assertThat(new Edge(2, 3, Bond.IMPLICIT).other(2), is(3));
    assertThat(new Edge(2, 3, Bond.IMPLICIT).other(3), is(2));
    assertThat(new Edge(3, 2, Bond.IMPLICIT).other(2), is(3));
    assertThat(new Edge(3, 2, Bond.IMPLICIT).other(3), is(2));
}