public void interpreterTest()
{
AddExpression addExpression = new AddExpression(new VarExpression(0), new VarExpression(2));
List <string> list = new List <string>();
list.Add("1");
list.Add("+");
list.Add("3");
list.Add("-");
list.Add("1");
int i = addExpression.interpreter(list);
Assert.AreEqual(4, i);
}