public void AddIsotopeToFormula()
{
ChemicalFormula formulaA = new ChemicalFormula("C2H3NO");
ChemicalFormula formulaB = new ChemicalFormula("C2H4NO");
Isotope h1 = PeriodicTable.GetElement("H")[1];
formulaA.Add(h1, 1);
Assert.AreEqual(formulaA, formulaB);
}