@Test public void benzene() throws Exception {

    Graph g = Graph.fromSmiles("c1ccccc1");
    Matching m = Matching.empty(g);
    ArbitraryMatching.initial(g,
                              m,
                              allOf(0, 1, 2, 3, 4, 5));
    assertThat(m.matches(),
               IsIterableWithSize.<Tuple>iterableWithSize(3));
    assertThat(m.matches(),
               hasItems(Tuple.of(0, 1),
                        Tuple.of(2, 3),
                        Tuple.of(4, 5)));
}