XmlSerializableConstraint.cs

// ****************************************************************
// Copyright 2008, Charlie Poole
// This is free software licensed under the NUnit license. You may
// obtain a copy of the license at http://nunit.org
// ****************************************************************

using System;
using System.IO;
using System.Xml.Serialization;

namespace NUnit.Framework.Constraints
{
    /// <summary>
    /// XmlSerializableConstraint tests whether 
    /// an object is serializable in XML format.
    /// </summary>
    public class XmlSerializableConstraint : Constraint
    {
        private XmlSerializer serializer;

        /// <summary>
        /// Test whether the constraint is satisfied by a given value
        /// </summary>
        /// <param name="actual">The value to be tested</param>
        /// <returns>True for success, false for failure</returns>
        public override bool Matches(object actual)
        {
            this.actual = actual;

            if (actual == null)
                throw new ArgumentException();

            MemoryStream stream = new MemoryStream();

            try
            {
                serializer = new XmlSerializer(actual.GetType());

                serializer.Serialize(stream, actual);

                stream.Seek(0, SeekOrigin.Begin);

                object value = serializer.Deserialize(stream);

                return value != null;
            }
            catch (NotSupportedException)
            {
                return false;
            }
            catch (InvalidOperationException)
            {
                return false;
            }
        }

        /// <summary>
        /// Write the constraint description to a MessageWriter
        /// </summary>
        /// <param name="writer">The writer on which the description is displayed</param>
        public override void WriteDescriptionTo(MessageWriter writer)
        {
            writer.Write("xml serializable");
        }

        /// <summary>
        /// Write the actual value for a failing constraint test to a
        /// MessageWriter. The default implementation simply writes
        /// the raw value of actual, leaving it to the writer to
        /// perform any formatting.
        /// </summary>
        /// <param name="writer">The writer on which the actual value is displayed</param>
        public override void WriteActualValueTo(MessageWriter writer)
        {
            writer.Write("<{0}>", actual.GetType().Name);
        }

        /// <summary>
        /// Returns the string representation of this constraint
        /// </summary>
        protected override string GetStringRepresentation()
        {
            return "<xmlserializable>";
        }
    }
}