@Test
public void tin_ii() {

    IAtomContainer container = new AtomContainer();
    IAtom atom = new Atom("Sn");
    atom.setValency(2);
    container.addAtom(atom);
    MDLValence.apply(container);
    assertThat(atom.getValency(), is(2));
    assertThat(atom.getImplicitHydrogenCount(), is(2));
}