@Test
public void testGetHeavyElements_IMolecularFormula() {

    IMolecularFormula formula = new MolecularFormula();
    formula.addIsotope(builder.newInstance(IIsotope.class, "C"), 10);
    formula.addIsotope(builder.newInstance(IIsotope.class, "H"), 16);
    Assert.assertEquals(1, MolecularFormulaManipulator.getHeavyElements(formula).size());
}