@Test public void furan() throws Exception {

    Graph g = Graph.fromSmiles("o1cccc1");
    Matching m = Matching.empty(g);
    ArbitraryMatching.initial(g, m,
                              allOf(1, 2, 3, 4));
    // note this matching is maximum
    assertThat(m.matches(),
               IsIterableWithSize.<Tuple>iterableWithSize(2));
    assertThat(m.matches(),
               hasItems(Tuple.of(1, 2),
                        Tuple.of(3, 4)));
}