@Test public void implHCount() throws Exception{

    Graph g = Graph.fromSmiles("C1NC=C[C]=C1");
    assertThat(g.implHCount(0), is(2));
    assertThat(g.implHCount(1), is(1));
    assertThat(g.implHCount(2), is(1));
    assertThat(g.implHCount(3), is(1));
    assertThat(g.implHCount(4), is(0));
    assertThat(g.implHCount(5), is(1));
}