public void ParseString()
{
ModelParser parser = new ModelParser("'foo'");
IExpression expression = parser.ParseExpression();
Assert.IsNotNull(expression);
Assert.IsInstanceOfType(expression, typeof(ConstantExpression));
ConstantExpression cexpression = (ConstantExpression)expression;
Assert.AreEqual("foo", cexpression.Value);
Assert.AreEqual("'foo'", expression.AsString());
}