@Test
public void htmlFormulaDoesNotAddSubscriptForSingleElements() {

    MolecularFormula formula = new MolecularFormula();
    formula.addIsotope(builder.newInstance(IIsotope.class, "C"), 1);
    formula.addIsotope(builder.newInstance(IIsotope.class, "H"), 4);
    Assert.assertEquals("CH<sub>4</sub>", MolecularFormulaManipulator.getHTML(formula));
}