public void ParseInteger()
{
Parser parser = new Parser("123.");
IExpression expression = parser.ParseExpression();
Assert.IsNotNull(expression);
Assert.IsInstanceOfType(expression, typeof(ConstantExpression));
ConstantExpression consexpression = (ConstantExpression)expression;
Assert.IsNotNull(consexpression.Value);
Assert.AreEqual(123, consexpression.Value);
Assert.IsNull(parser.ParseExpression());
}