void CheckSubExpression(string from, string to)
{
if (from == null)
{
throw new ArgumentNullException("from");
}
if (to == null)
{
throw new ArgumentNullException("to");
}
MacroScopeParser parser = Factory.CreateParser(from);
IExpression expression = parser.subExpression();
Assert.IsNotNull(expression);
Assert.AreEqual(to, TestUtil.Stringify(expression));
}