@Test
public void carbon_cation_doubleBonded() {

    IAtomContainer container = new AtomContainer();
    IAtom c1 = new Atom("C");
    IAtom c2 = new Atom("C");
    c1.setFormalCharge(-1);
    container.addAtom(c1);
    container.addAtom(c2);
    container.addBond(0, 1, IBond.Order.DOUBLE);
    MDLValence.apply(container);
    assertThat(c1.getValency(), is(3));
    assertThat(c1.getImplicitHydrogenCount(), is(1));
    assertThat(c2.getValency(), is(4));
    assertThat(c2.getImplicitHydrogenCount(), is(2));
}