How to Compare two object in Unit test? How to Compare two collection in Unit test?

Question

public class Student
    {
        private string _name;

        public string Name
        {
            get { return _name; }
            set { _name = value; }
        }

        private int id;

        public int ID
        {
            get { return id; }
            set { id = value; }
        }
    }



        Student st1 = new Student();
        st1.ID = 20;
        st1.Name = "ligaoren";


        Student st2 = new Student();
        st2.ID = 20;
        st2.Name = "ligaoren";

        Assert.AreEqual<Student>(st1, st2);// How to Compare two object in Unit test?

How to Compare two collection in Unitest?

Answer 1

Maybe you need to add an public bool Equals(object o) to the class.

Answer 2

You should provide an override of Object.Equals and Object.GetHashCode:

public override bool Equals(object obj) {
    Student other = obj as Student;
    if(other == null) {
        return false;
    }
    return (this.Name == other.Name) && (this.ID == other.ID);
}

public override int GetHashCode() {
    return 33 * Name.GetHashCode() + ID.GetHashCode();
}

As for checking if two collections are equal, use Enumerable.SequenceEqual:

// first and second are IEnumerable<T>
Assert.IsTrue(first.SequenceEqual(second)); 

Note that you might need to use the overload that accepts an IEqualityComparer<T>.

Answer 3

Here's an NUnit 2.4.6 custom constraint we use for comparing complex graphs. It supports embedded collections, parent references, setting tolerance for numeric comparisons, identifying field names to ignore (even deep within the hierarchy), and decorating types to be always ignored.

I'm sure this code can be adapted to be used outside NUnit, the bulk of the code isn't dependent on NUnit.

We use this in thousands of unit tests.

using System;
using System.Collections;
using System.Collections.Generic;
using System.Reflection;
using System.Text;
using NUnit.Framework;
using NUnit.Framework.Constraints;

namespace Tests
{
    public class ContentsEqualConstraint : Constraint
    {
        private readonly object expected;
        private Constraint failedEquality;
        private string expectedDescription;
        private string actualDescription;

        private readonly Stack<string> typePath = new Stack<string>();
        private string typePathExpanded;

        private readonly HashSet<string> _ignoredNames = new HashSet<string>();
        private readonly HashSet<Type> _ignoredTypes = new HashSet<Type>();
        private readonly LinkedList<Type> _ignoredInterfaces = new LinkedList<Type>();
        private readonly LinkedList<string> _ignoredSuffixes = new LinkedList<string>();
        private readonly IDictionary<Type, Func<object, object, bool>> _predicates = new Dictionary<Type, Func<object, object, bool>>();

        private bool _withoutSort;
        private int _maxRecursion = int.MaxValue;

        private readonly HashSet<VisitedComparison> _visitedObjects = new HashSet<VisitedComparison>();

        private static readonly HashSet<string> _globallyIgnoredNames = new HashSet<string>();
        private static readonly HashSet<Type> _globallyIgnoredTypes = new HashSet<Type>();
        private static readonly LinkedList<Type> _globallyIgnoredInterfaces = new LinkedList<Type>();

        private static object _regionalTolerance;

        public ContentsEqualConstraint(object expectedValue)
        {
            expected = expectedValue;
        }

        public ContentsEqualConstraint Comparing<T>(Func<T, T, bool> predicate)
        {
            Type t = typeof (T);

            if (predicate == null)
            {
                _predicates.Remove(t);
            }
            else
            {
                _predicates[t] = (x, y) => predicate((T) x, (T) y);
            }
            return this;
        }

        public ContentsEqualConstraint Ignoring(string fieldName)
        {
            _ignoredNames.Add(fieldName);
            return this;
        }

        public ContentsEqualConstraint Ignoring(Type fieldType)
        {
            if (fieldType.IsInterface)
            {
                _ignoredInterfaces.AddFirst(fieldType);
            }
            else
            {
                _ignoredTypes.Add(fieldType);
            }
            return this;
        }

        public ContentsEqualConstraint IgnoringSuffix(string suffix)
        {
            if (string.IsNullOrEmpty(suffix))
            {
                throw new ArgumentNullException("suffix");
            }
            _ignoredSuffixes.AddLast(suffix);
            return this;
        }

        public ContentsEqualConstraint WithoutSort()
        {
            _withoutSort = true;
            return this;
        }

        public ContentsEqualConstraint RecursingOnly(int levels)
        {
            _maxRecursion = levels;
            return this;
        }

        public static void GlobalIgnore(string fieldName)
        {
            _globallyIgnoredNames.Add(fieldName);
        }

        public static void GlobalIgnore(Type fieldType)
        {
            if (fieldType.IsInterface)
            {
                _globallyIgnoredInterfaces.AddFirst(fieldType);
            }
            else
            {
                _globallyIgnoredTypes.Add(fieldType);
            }
        }

        public static IDisposable RegionalIgnore(string fieldName)
        {
            return new RegionalIgnoreTracker(fieldName);
        }

        public static IDisposable RegionalIgnore(Type fieldType)
        {
            return new RegionalIgnoreTracker(fieldType);
        }

        public static IDisposable RegionalWithin(object tolerance)
        {
            return new RegionalWithinTracker(tolerance);
        }

        public override bool Matches(object actualValue)
        {
            typePathExpanded = null;
            actual = actualValue;
            return Matches(expected, actualValue);
        }

        private bool Matches(object expectedValue, object actualValue)
        {

            bool matches = true;

            if (!MatchesNull(expectedValue, actualValue, ref matches))
            {
                return matches;
            }
            // DatesEqualConstraint supports tolerance in dates but works as equal constraint for everything else
            Constraint eq = new DatesEqualConstraint(expectedValue).Within(tolerance ?? _regionalTolerance);
            if (eq.Matches(actualValue))
            {
                return true;
            }

            if (MatchesVisited(expectedValue, actualValue, ref matches))
            {
                if (MatchesDictionary(expectedValue, actualValue, ref matches) &&
                    MatchesList(expectedValue, actualValue, ref matches) &&
                    MatchesType(expectedValue, actualValue, ref matches) &&
                    MatchesPredicate(expectedValue, actualValue, ref matches))
                {
                    MatchesFields(expectedValue, actualValue, eq, ref matches);
                }
            }

            return matches;
        }

        private bool MatchesNull(object expectedValue, object actualValue, ref bool matches)
        {
            if (IsNullEquivalent(expectedValue))
            {
                expectedValue = null;
            }

            if (IsNullEquivalent(actualValue))
            {
                actualValue = null;
            }

            if (expectedValue == null && actualValue == null)
            {
                matches = true;
                return false;
            }

            if (expectedValue == null)
            {
                expectedDescription = "null";
                actualDescription = "NOT null";
                matches = Failure;
                return false;
            }

            if (actualValue == null)
            {
                expectedDescription = "not null";
                actualDescription = "null";
                matches = Failure;
                return false;
            }

            return true;
        }

        private bool MatchesType(object expectedValue, object actualValue, ref bool matches)
        {
            Type expectedType = expectedValue.GetType();
            Type actualType = actualValue.GetType();

            if (expectedType != actualType)
            {
                try
                {
                    Convert.ChangeType(actualValue, expectedType);
                }
                catch(InvalidCastException)             
                {
                    expectedDescription = expectedType.FullName;
                    actualDescription = actualType.FullName;
                    matches = Failure;
                    return false;
                }

            }
            return true;
        }

        private bool MatchesPredicate(object expectedValue, object actualValue, ref bool matches)
        {
            Type t = expectedValue.GetType();
            Func<object, object, bool> predicate;

            if (_predicates.TryGetValue(t, out predicate))
            {
                matches = predicate(expectedValue, actualValue);
                return false;
            }
            return true;
        }

        private bool MatchesVisited(object expectedValue, object actualValue, ref bool matches)
        {
            var c = new VisitedComparison(expectedValue, actualValue);

            if (_visitedObjects.Contains(c))
            {
                matches = true;
                return false;
            }

            _visitedObjects.Add(c);

            return true;
        }

        private bool MatchesDictionary(object expectedValue, object actualValue, ref bool matches)
        {
            if (expectedValue is IDictionary && actualValue is IDictionary)
            {
                var expectedDictionary = (IDictionary)expectedValue;
                var actualDictionary = (IDictionary)actualValue;

                if (expectedDictionary.Count != actualDictionary.Count)
                {
                    expectedDescription = expectedDictionary.Count + " item dictionary";
                    actualDescription = actualDictionary.Count + " item dictionary";
                    matches = Failure;
                    return false;
                }

                foreach (DictionaryEntry expectedEntry in expectedDictionary)
                {
                    if (!actualDictionary.Contains(expectedEntry.Key))
                    {
                        expectedDescription = expectedEntry.Key + " exists";
                        actualDescription = expectedEntry.Key + " does not exist";
                        matches = Failure;
                        return false;
                    }
                    if (CanRecurseFurther)
                    {
                        typePath.Push(expectedEntry.Key.ToString());
                        if (!Matches(expectedEntry.Value, actualDictionary[expectedEntry.Key]))
                        {
                            matches = Failure;
                            return false;
                        }
                        typePath.Pop();
                    }
                }
                matches = true;
                return false;
            }
            return true;
        }

        private bool MatchesList(object expectedValue, object actualValue, ref bool matches)
        {
            if (!(expectedValue is IList && actualValue is IList))
            {
                return true;
            }

            var expectedList = (IList) expectedValue;
            var actualList = (IList) actualValue;

            if (!Matches(expectedList.Count, actualList.Count))
            {
                matches = false;
            }
            else
            {
                if (CanRecurseFurther)
                {
                    int max = expectedList.Count;

                    if (max != 0 && !_withoutSort)
                    {
                        SafeSort(expectedList);
                        SafeSort(actualList);
                    }

                    for (int i = 0; i < max; i++)
                    {
                        typePath.Push(i.ToString());

                        if (!Matches(expectedList[i], actualList[i]))
                        {
                            matches = false;
                            return false;
                        }
                        typePath.Pop();
                    }
                }
                matches = true;
            }
            return false;
        }

        private void MatchesFields(object expectedValue, object actualValue, Constraint equalConstraint, ref bool matches)
        {
            Type expectedType = expectedValue.GetType();

            FieldInfo[] fields = expectedType.GetFields(BindingFlags.Instance | BindingFlags.NonPublic);

            // should have passed the EqualConstraint check
            if (expectedType.IsPrimitive ||
                expectedType == typeof(string) ||
                expectedType == typeof(Guid) ||
                fields.Length == 0)
            {
                failedEquality = equalConstraint;
                matches = Failure;
                return;
            }

            if (expectedType == typeof(DateTime))
            {
                var expectedDate = (DateTime)expectedValue;
                var actualDate = (DateTime)actualValue;

                if (Math.Abs((expectedDate - actualDate).TotalSeconds) > 3.0)
                {
                    failedEquality = equalConstraint;
                    matches = Failure;
                    return;
                }
                matches = true;
                return;
            }

            if (CanRecurseFurther)
            {
                while(true)
                {
                    foreach (FieldInfo field in fields)
                    {
                        if (!Ignore(field))
                        {
                            typePath.Push(field.Name);
                            if (!Matches(GetValue(field, expectedValue), GetValue(field, actualValue)))
                            {
                                matches = Failure;
                                return;
                            }
                            typePath.Pop();
                        }
                    }
                    expectedType = expectedType.BaseType;
                    if (expectedType == null)
                    {
                        break;
                    }
                    fields = expectedType.GetFields(BindingFlags.Instance | BindingFlags.NonPublic);
                }
            }
            matches = true;
            return;
        }

        private bool Ignore(FieldInfo field)
        {
            if (_ignoredNames.Contains(field.Name) ||
                _ignoredTypes.Contains(field.FieldType) ||
                _globallyIgnoredNames.Contains(field.Name) ||
                _globallyIgnoredTypes.Contains(field.FieldType) ||
                field.GetCustomAttributes(typeof (IgnoreContentsAttribute), false).Length != 0)
            {
                return true;
            }

            foreach(string ignoreSuffix in _ignoredSuffixes)
            {
                if (field.Name.EndsWith(ignoreSuffix))
                {
                    return true;
                }
            }

            foreach (Type ignoredInterface in _ignoredInterfaces)
            {
                if (ignoredInterface.IsAssignableFrom(field.FieldType))
                {
                    return true;
                }
            }
            return false;
        }

        private static bool Failure
        {
            get
            {
                return false;
            }
        }

        private static bool IsNullEquivalent(object value)
        {
            return value == null ||
                    value == DBNull.Value ||
                   (value is int && (int) value == int.MinValue) ||
                   (value is double && (double) value == double.MinValue) ||
                   (value is DateTime && (DateTime) value == DateTime.MinValue) ||
                   (value is Guid && (Guid) value == Guid.Empty) ||
                   (value is IList && ((IList)value).Count == 0);
        }

        private static object GetValue(FieldInfo field, object source)
        {
            try
            {
                return field.GetValue(source);
            }
            catch(Exception ex)
            {
                return ex;
            }
        }

        public override void WriteMessageTo(MessageWriter writer)
        {
            if (TypePath.Length != 0)
            {
                writer.WriteLine("Failure on " + TypePath);
            }

            if (failedEquality != null)
            {
                failedEquality.WriteMessageTo(writer);
            }
            else
            {
                base.WriteMessageTo(writer);
            }
        }
        public override void WriteDescriptionTo(MessageWriter writer)
        {
            writer.Write(expectedDescription);
        }

        public override void WriteActualValueTo(MessageWriter writer)
        {
            writer.Write(actualDescription);
        }

        private string TypePath
        {
            get
            {
                if (typePathExpanded == null)
                {
                    string[] p = typePath.ToArray();
                    Array.Reverse(p);
                    var text = new StringBuilder(128);
                    bool isFirst = true;
                    foreach(string part in p)
                    {
                        if (isFirst)
                        {
                            text.Append(part);
                            isFirst = false;
                        }
                        else
                        {
                            int i;
                            if (int.TryParse(part, out i))
                            {
                                text.Append("[" + part + "]");
                            }
                            else
                            {
                                text.Append("." + part);
                            }
                        }
                    }
                    typePathExpanded = text.ToString();
                }
                return typePathExpanded;
            }
        }

        private bool CanRecurseFurther
        {
            get
            {
                return typePath.Count < _maxRecursion;
            }
        }

        private static bool SafeSort(IList list)
        {
            if (list == null)
            {
                return false;
            }

            if (list.Count < 2)
            {
                return true;
            }

            try
            {
                object first = FirstNonNull(list) as IComparable;
                if (first == null)
                {
                    return false;
                }

                if (list is Array)
                {
                    Array.Sort((Array)list);
                    return true;
                }
                return CallIfExists(list, "Sort");
            }
            catch
            {
                return false;
            }
        }

        private static object FirstNonNull(IEnumerable enumerable)
        {
            if (enumerable == null)
            {
                throw new ArgumentNullException("enumerable");
            }
            foreach (object item in enumerable)
            {
                if (item != null)
                {
                    return item;
                }
            }
            return null;
        }

        private static bool CallIfExists(object instance, string method)
        {
            if (instance == null)
            {
                throw new ArgumentNullException("instance");
            }
            if (String.IsNullOrEmpty(method))
            {
                throw new ArgumentNullException("method");
            }
            Type target = instance.GetType();
            MethodInfo m = target.GetMethod(method, new Type[0]);
            if (m != null)
            {
                m.Invoke(instance, null);
                return true;
            }
            return false;
        }

        #region VisitedComparison Helper

        private class VisitedComparison
        {
            private readonly object _expected;
            private readonly object _actual;

            public VisitedComparison(object expected, object actual)
            {
                _expected = expected;
                _actual = actual;
            }

            public override int GetHashCode()
            {
                return GetHashCode(_expected) ^ GetHashCode(_actual);
            }

            private static int GetHashCode(object o)
            {
                if (o == null)
                {
                    return 0;
                }
                return o.GetHashCode();
            }

            public override bool Equals(object obj)
            {
                if (obj == null)
                {
                    return false;
                }

                if (obj.GetType() != typeof(VisitedComparison))
                {
                    return false;
                }

                var other = (VisitedComparison) obj;
                return _expected == other._expected &&
                       _actual == other._actual;
            }
        }

        #endregion

        #region RegionalIgnoreTracker Helper

        private class RegionalIgnoreTracker : IDisposable
        {
            private readonly string _fieldName;
            private readonly Type _fieldType;

            public RegionalIgnoreTracker(string fieldName)
            {
                if (!_globallyIgnoredNames.Add(fieldName))
                {
                    _globallyIgnoredNames.Add(fieldName);
                    _fieldName = fieldName;
                }
            }

            public RegionalIgnoreTracker(Type fieldType)
            {
                if (!_globallyIgnoredTypes.Add(fieldType))
                {
                    _globallyIgnoredTypes.Add(fieldType);
                    _fieldType = fieldType;
                }
            }

            public void Dispose()
            {
                if (_fieldName != null)
                {
                    _globallyIgnoredNames.Remove(_fieldName);
                }
                if (_fieldType != null)
                {
                    _globallyIgnoredTypes.Remove(_fieldType);
                }
            }
        }

        #endregion

        #region RegionalWithinTracker Helper

        private class RegionalWithinTracker : IDisposable
        {
            public RegionalWithinTracker(object tolerance)
            {
                _regionalTolerance = tolerance;
            }

            public void Dispose()
            {
                _regionalTolerance = null;
            }
        }

        #endregion

        #region IgnoreContentsAttribute

        [AttributeUsage(AttributeTargets.Field)]
        public sealed class IgnoreContentsAttribute : Attribute
        {
        }

        #endregion
    }
    public class DatesEqualConstraint : EqualConstraint
    {
        private readonly object _expected;

        public DatesEqualConstraint(object expectedValue) : base(expectedValue)
        {
            _expected = expectedValue;
        }

        public override bool Matches(object actualValue)
        {
            if (tolerance != null && tolerance is TimeSpan)
            {
                if (_expected is DateTime && actualValue is DateTime)
                {
                    var expectedDate = (DateTime) _expected;
                    var actualDate = (DateTime) actualValue;
                    var toleranceSpan = (TimeSpan) tolerance;

                    if ((actualDate - expectedDate).Duration() <= toleranceSpan)
                    {
                        return true;
                    }
                }
                tolerance = null;
            }
            return base.Matches(actualValue);
        }
    }
}

Answer 4

What you are looking for is what in xUnit Test Patterns is called Test-Specific Equality.

While you can sometimes choose to override the Equals method, this may lead to Equality Pollution because the implementation you need to the test may not be the correct one for the type in general.

For example, Domain-Driven Design distinguishes between Entities and Value Objects, and those have vastly different equality semantics.

When this is the case, you can write a custom comparison for the type in question.

If you get tired doing this, AutoFixture's Likeness class offers general-purpose Test-Specific Equality. With your Student class, this would allow you to write a test like this:

[TestMethod]
public void VerifyThatStudentAreEqual()
{
    Student st1 = new Student();
    st1.ID = 20;
    st1.Name = "ligaoren";

    Student st2 = new Student();
    st2.ID = 20;
    st2.Name = "ligaoren";

    var expectedStudent = new Likeness<Student, Student>(st1);

    Assert.AreEqual(expectedStudent, st2);
}

This doesn't require you to override Equals on Student.

Likeness performs a semantic comparison, so it can also compare two different types as long as they are semantically similar.

Answer 5

http://www.infoq.com/articles/Equality-Overloading-DotNET

This article may be usefull , I solve this problem just using refcetion dump all filed out; Then we just need compare two strings.

Code Here:

 /// <summary>
    /// output all properties and values of obj
    /// </summary>
    /// <param name="obj"></param>
    /// <param name="separator">default as ";"</param>
    /// <returns>properties and values of obj,with specified separator </returns>
    /// <Author>ligaoren</Author>
    public static string Dump(object obj, string separator)
    {
        try
        {
            if (obj == null)
            {
                return string.Empty;
            }
            if (string.IsNullOrEmpty(separator))
            {
                separator = ";";
            }
            Type t = obj.GetType();
            StringBuilder info = new StringBuilder(t.Name).Append(" Values : ");
            foreach (PropertyInfo item in t.GetProperties())
            {
                object value = t.GetProperty(item.Name).GetValue(obj, null);
                info.AppendFormat("[{0}:{1}]{2}", item.Name, value, separator);
            }
            return info.ToString();
        }
        catch (Exception ex)
        {
            log.Error("Dump Exception", ex);
            return string.Empty;
        }
    }