@Test
public void testSmallMass() throws Exception {

    IsotopeFactory ifac = Isotopes.getInstance();
    IIsotope c = ifac.getMajorIsotope("C");
    IIsotope h = ifac.getMajorIsotope("H");
    IIsotope n = ifac.getMajorIsotope("N");
    IIsotope o = ifac.getMajorIsotope("O");
    MolecularFormulaRange mfRange = new MolecularFormulaRange();
    mfRange.addIsotope(c, 0, 20);
    mfRange.addIsotope(h, 0, 30);
    mfRange.addIsotope(o, 0, 15);
    mfRange.addIsotope(n, 0, 10);
    double minMass = 115.08714 - 0.0001;
    double maxMass = 115.08714 + 0.0001;
    MolecularFormulaGenerator gen = new MolecularFormulaGenerator(builder,
            minMass, maxMass, mfRange);
    IMolecularFormulaSet mfSet = gen.getAllFormulas();
    Assert.assertNotNull(mfSet);
    Assert.assertEquals(1, mfSet.size());
    Assert.assertEquals("C5H11N2O", MolecularFormulaManipulator
            .getString(mfSet.getMolecularFormula(0)));
}