public void AddElementToFormula()
{
ChemicalFormula formulaA = new ChemicalFormula("C2H3NO");
ChemicalFormula formulaB = new ChemicalFormula("C2H3N2O");
Element n = PeriodicTable.GetElement("N");
formulaA.Add(n, 1);
Assert.AreEqual(formulaA, formulaB);
}