/src/NUnit/framework/Constraints/TypeConstraints.cs

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

// Copyright 2007, 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;



namespace NUnit.Framework.Constraints

{

    /// <summary>

    /// TypeConstraint is the abstract base for constraints

    /// that take a Type as their expected value.

    /// </summary>

    public abstract class TypeConstraint : Constraint

    {

        /// <summary>

        /// The expected Type used by the constraint

        /// </summary>

        protected Type expectedType;



        /// <summary>

        /// Construct a TypeConstraint for a given Type

        /// </summary>

        /// <param name="type"></param>

        public TypeConstraint(Type type) : base(type)

        {

            this.expectedType = type;

        }



        /// <summary>

        /// Write the actual value for a failing constraint test to a

        /// MessageWriter. TypeConstraints override this method to write

        /// the name of the type.

        /// </summary>

        /// <param name="writer">The writer on which the actual value is displayed</param>

		public override void WriteActualValueTo(MessageWriter writer)

		{

			writer.WriteActualValue( actual == null ? null : actual.GetType() ); 

		}

	}



    /// <summary>

    /// ExactTypeConstraint is used to test that an object

    /// is of the exact type provided in the constructor

    /// </summary>

    public class ExactTypeConstraint : TypeConstraint

    {

        /// <summary>

        /// Construct an ExactTypeConstraint for a given Type

        /// </summary>

        /// <param name="type">The expected Type.</param>

        public ExactTypeConstraint(Type type) : base( type ) 

        {

            this.DisplayName = "typeof";

        }



        /// <summary>

        /// Test that an object is of the exact type specified

        /// </summary>

        /// <param name="actual">The actual value.</param>

        /// <returns>True if the tested object is of the exact type provided, otherwise false.</returns>

        public override bool Matches(object actual)

        {

            this.actual = actual;

            return actual != null && actual.GetType() == this.expectedType;

        }



        /// <summary>

        /// Write the description of this constraint to a MessageWriter

        /// </summary>

        /// <param name="writer">The MessageWriter to use</param>

        public override void WriteDescriptionTo(MessageWriter writer)

        {

            writer.WriteExpectedValue(expectedType);

        }

    }



    /// <summary>

    /// InstanceOfTypeConstraint is used to test that an object

    /// is of the same type provided or derived from it.

    /// </summary>

    public class InstanceOfTypeConstraint : TypeConstraint

    {

        /// <summary>

        /// Construct an InstanceOfTypeConstraint for the type provided

        /// </summary>

        /// <param name="type">The expected Type</param>

        public InstanceOfTypeConstraint(Type type) : base(type) 

        {

            this.DisplayName = "instanceof";

        }



        /// <summary>

        /// Test whether an object is of the specified type or a derived type

        /// </summary>

        /// <param name="actual">The object to be tested</param>

        /// <returns>True if the object is of the provided type or derives from it, otherwise false.</returns>

        public override bool Matches(object actual)

        {

            this.actual = actual;

            return actual != null && expectedType.IsInstanceOfType(actual);

        }



        /// <summary>

        /// Write a description of this constraint to a MessageWriter

        /// </summary>

        /// <param name="writer">The MessageWriter to use</param>

        public override void WriteDescriptionTo(MessageWriter writer)

        {

            writer.WritePredicate("instance of");

            writer.WriteExpectedValue(expectedType);

        }

	}



    /// <summary>

    /// AssignableFromConstraint is used to test that an object

    /// can be assigned from a given Type.

    /// </summary>

    public class AssignableFromConstraint : TypeConstraint

    {

        /// <summary>

        /// Construct an AssignableFromConstraint for the type provided

        /// </summary>

        /// <param name="type"></param>

        public AssignableFromConstraint(Type type) : base(type) { }



        /// <summary>

        /// Test whether an object can be assigned from the specified type

        /// </summary>

        /// <param name="actual">The object to be tested</param>

        /// <returns>True if the object can be assigned a value of the expected Type, otherwise false.</returns>

        public override bool Matches(object actual)

        {

            this.actual = actual;

            return actual != null && actual.GetType().IsAssignableFrom(expectedType);

        }



        /// <summary>

        /// Write a description of this constraint to a MessageWriter

        /// </summary>

        /// <param name="writer">The MessageWriter to use</param>

        public override void WriteDescriptionTo(MessageWriter writer)

        {

            writer.WritePredicate("assignable from");

            writer.WriteExpectedValue(expectedType);

        }

    }



    /// <summary>

    /// AssignableToConstraint is used to test that an object

    /// can be assigned to a given Type.

    /// </summary>

    public class AssignableToConstraint : TypeConstraint

    {

        /// <summary>

        /// Construct an AssignableToConstraint for the type provided

        /// </summary>

        /// <param name="type"></param>

        public AssignableToConstraint(Type type) : base(type) { }



        /// <summary>

        /// Test whether an object can be assigned to the specified type

        /// </summary>

        /// <param name="actual">The object to be tested</param>

        /// <returns>True if the object can be assigned a value of the expected Type, otherwise false.</returns>

        public override bool Matches(object actual)

        {

            this.actual = actual;

            return actual != null && expectedType.IsAssignableFrom(actual.GetType());

        }



        /// <summary>

        /// Write a description of this constraint to a MessageWriter

        /// </summary>

        /// <param name="writer">The MessageWriter to use</param>

        public override void WriteDescriptionTo(MessageWriter writer)

        {

            writer.WritePredicate("assignable to");

            writer.WriteExpectedValue(expectedType);

        }

    }

}