@Test
public void testSulphurAcidGroup() throws Exception {

    SmilesParser sp = new SmilesParser(SilentChemObjectBuilder.getInstance());
    IAtomContainer mol = sp.parseSmiles("OS(=O)(=O)O");
    IntegerResult result = (IntegerResult) descriptor.calculate(mol).getValue();
    Assert.assertEquals(2, result.intValue());
}