/src/NUnit/framework/Constraints/BasicConstraints.cs

  1// ****************************************************************
  2// Copyright 2008, Charlie Poole
  3// This is free software licensed under the NUnit license. You may
  4// obtain a copy of the license at http://nunit.org
  5// ****************************************************************
  6using System;
  7
  8namespace NUnit.Framework.Constraints
  9{
 10    /// <summary>
 11    /// BasicConstraint is the abstract base for constraints that
 12    /// perform a simple comparison to a constant value.
 13    /// </summary>
 14    public abstract class BasicConstraint : Constraint
 15    {
 16        private object expected;
 17        private string description;
 18
 19        /// <summary>
 20        /// Initializes a new instance of the <see cref="T:BasicConstraint"/> class.
 21        /// </summary>
 22        /// <param name="expected">The expected.</param>
 23        /// <param name="description">The description.</param>
 24        public BasicConstraint(object expected, string description)
 25        {
 26            this.expected = expected;
 27            this.description = description;
 28        }
 29
 30        /// <summary>
 31        /// Test whether the constraint is satisfied by a given value
 32        /// </summary>
 33        /// <param name="actual">The value to be tested</param>
 34        /// <returns>True for success, false for failure</returns>
 35        public override bool Matches(object actual)
 36        {
 37            this.actual = actual;
 38
 39            if (actual == null && expected == null)
 40                return true;
 41
 42            if (actual == null || expected == null)
 43                return false;
 44            
 45            return expected.Equals(actual);
 46        }
 47
 48        /// <summary>
 49        /// Write the constraint description to a MessageWriter
 50        /// </summary>
 51        /// <param name="writer">The writer on which the description is displayed</param>
 52        public override void WriteDescriptionTo(MessageWriter writer)
 53        {
 54            writer.Write(description);
 55        }
 56    }
 57
 58    /// <summary>
 59    /// NullConstraint tests that the actual value is null
 60    /// </summary>
 61    public class NullConstraint : BasicConstraint
 62    {
 63        /// <summary>
 64        /// Initializes a new instance of the <see cref="T:NullConstraint"/> class.
 65        /// </summary>
 66        public NullConstraint() : base(null, "null") { }
 67    }
 68
 69    /// <summary>
 70    /// TrueConstraint tests that the actual value is true
 71    /// </summary>
 72    public class TrueConstraint : BasicConstraint
 73    {
 74        /// <summary>
 75        /// Initializes a new instance of the <see cref="T:TrueConstraint"/> class.
 76        /// </summary>
 77        public TrueConstraint() : base(true, "True") { }
 78    }
 79
 80    /// <summary>
 81    /// FalseConstraint tests that the actual value is false
 82    /// </summary>
 83    public class FalseConstraint : BasicConstraint
 84    {
 85        /// <summary>
 86        /// Initializes a new instance of the <see cref="T:FalseConstraint"/> class.
 87        /// </summary>
 88        public FalseConstraint() : base(false, "False") { }
 89    }
 90
 91    /// <summary>
 92    /// NaNConstraint tests that the actual value is a double or float NaN
 93    /// </summary>
 94    public class NaNConstraint : Constraint
 95    {
 96        /// <summary>
 97        /// Test that the actual value is an NaN
 98        /// </summary>
 99        /// <param name="actual"></param>
100        /// <returns></returns>
101        public override bool Matches(object actual)
102        {
103            this.actual = actual;
104
105            return actual is double && double.IsNaN((double)actual)
106                || actual is float && float.IsNaN((float)actual);
107        }
108
109        /// <summary>
110        /// Write the constraint description to a specified writer
111        /// </summary>
112        /// <param name="writer"></param>
113        public override void WriteDescriptionTo(MessageWriter writer)
114        {
115            writer.Write("NaN");
116        }
117    }
118}