@Test
public void tin_iv() {

    IAtomContainer container = new AtomContainer();
    IAtom atom = new Atom("Sn");
    atom.setValency(4);
    IAtom hydrogen = new Atom("H");
    container.addAtom(atom);
    container.addAtom(hydrogen);
    container.addBond(0, 1, IBond.Order.SINGLE);
    MDLValence.apply(container);
    assertThat(atom.getValency(), is(4));
    assertThat(atom.getImplicitHydrogenCount(), is(3)); // 4 - explicit H
}