@Test
public void testDoubleCharge() throws ClassNotFoundException, CDKException, Exception {

    IRule rule = new NitrogenRule();
    IMolecularFormula formula = MolecularFormulaManipulator.getMolecularFormula("C22H34N2S2", builder);
    formula.setCharge(2);
    Assert.assertEquals(1.0, rule.validate(formula), 0.0001);
}