@Test
public void testGetTotalNaturalAbundance_IMolecularFormula2() throws Exception {

    IMolecularFormula formula1 = new MolecularFormula();
    IIsotope br1 = builder.newInstance(IIsotope.class, "Br");
    br1.setNaturalAbundance(49.31);
    IIsotope br2 = builder.newInstance(IIsotope.class, "Br");
    br2.setNaturalAbundance(50.69);
    formula1.addIsotope(br1);
    formula1.addIsotope(br2);
    Assert.assertEquals(2, formula1.getIsotopeCount(), 0.000001);
    double totalAbudance = MolecularFormulaManipulator.getTotalNaturalAbundance(formula1);
    Assert.assertEquals(0.24995235, totalAbudance, 0.000001);
}