public void EvaluateDecimal_Subtraction(string result, string a, string b)
{
var parser = new Parser();
ParserResult res = parser.Parse(String.Format("{0} - {1}", a, b));
var expected = decimal.Parse(result, System.Globalization.CultureInfo.InvariantCulture);
Assert.AreEqual(expected, res.EvaluateDecimal());
}