@Test
public void testIsotopes() {

    MolecularFormulaRange mfRange = new MolecularFormulaRange();
    mfRange.addIsotope(builder.newInstance(IIsotope.class, "C"), 0, 10);
    mfRange.addIsotope(builder.newInstance(IIsotope.class, "F"), 0, 10);
    Iterator<IIsotope> istoIter = mfRange.isotopes().iterator();
    int counter = 0;
    while (istoIter.hasNext()) {
        istoIter.next();
        counter++;
    }
    Assert.assertEquals(2, counter);
}