@Test
public void testRing() throws Exception {

    sp = new SmilesParser(SilentChemObjectBuilder.getInstance());
    IAtomContainer mol = sp.parseSmiles("C1CCCC1CCC2CCCNC2");
    addExplicitHydrogens(mol);
    DescriptorValue dv = descriptor.calculate(mol);
    Assert.assertNotNull(dv);
}