/src/NUnit/framework/Constraints/PredicateConstraint.cs

// ****************************************************************

// Copyright 2009, Charlie Poole

// This is free software licensed under the NUnit license. You may

// obtain a copy of the license at http://nunit.org

// ****************************************************************



#if NET_2_0

using System;

using System.Collections.Generic;



namespace NUnit.Framework.Constraints

{

    /// <summary>

    /// Predicate constraint wraps a Predicate in a constraint,

    /// returning success if the predicate is true.

    /// </summary>

    public class PredicateConstraint<T> : Constraint

    {

        Predicate<T> predicate;



        /// <summary>

        /// Construct a PredicateConstraint from a predicate

        /// </summary>

        public PredicateConstraint(Predicate<T> predicate)

        {

            this.predicate = predicate;

        }



        /// <summary>

        /// Determines whether the predicate succeeds when applied

        /// to the actual value.

        /// </summary>

        public override bool Matches(object actual)

        {

            this.actual = actual;



            if (!(actual is T))

                throw new ArgumentException("The actual value is not of type " + typeof(T).Name, "actual");



            return predicate((T)actual);

        }



        /// <summary>

        /// Writes the description to a MessageWriter

        /// </summary>

        public override void WriteDescriptionTo(MessageWriter writer)

        {

            writer.WritePredicate("value matching");

            writer.Write(predicate.Method.Name.StartsWith("<")

                ? "lambda expression"

                : predicate.Method.Name);

        }

    }

}

#endif