@Test public void furan_2() throws Exception {

    Graph g = Graph.fromSmiles("c1ccoc1");
    Matching m = Matching.empty(g);
    ArbitraryMatching.initial(g,
                              m,
                              allOf(0, 1, 2, 4));
    assertThat(m.matches(),
               IsIterableWithSize.<Tuple>iterableWithSize(1));
    assertThat(m.matches(),
               hasItem(Tuple.of(0, 1)));
}