如何在单元测试中比较两个对象？

Question

public class Student
{
    public string Name { get; set; }
    public int ID { get; set; }
}

...

var st1 = new Student
{
    ID = 20,
    Name = "ligaoren",
};

var st2 = new Student
{
    ID = 20,
    Name = "ligaoren",
};

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

如何比较Unitest中的两个集合？

Answer 1

您正在寻找的是xUnit测试模式中称为测试特定平等的内容 。

虽然您有时可以选择覆盖Equals方法，但这可能会导致Equality污染，因为测试所需的实现可能不是一般类型的正确实现。

例如， 域驱动设计区分实体和值对象 ，并且那些具有截然不同的等式语义。

在这种情况下，您可以为相关类型编写自定义比较。

如果你厌倦这样做， AutoFixture的Likeness类提供通用的测试特定平等。 使用您的Student类，这将允许您编写如下测试：

[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);
}

这不要求您在学生上覆盖等于。

Likeness执行语义比较，因此只要它们在语义上相似，它也可以比较两种不同的类型。

Answer 2

如果比较公共成员足以满足您的用例，只需将对象插入JSON并比较结果字符串：

var js = new JavaScriptSerializer();
Assert.AreEqual(js.Serialize(st1), js.Serialize(st2));

JavaScriptSerializer类

优点

• 需要最少的代码，零努力，没有初步设置
• 使用嵌套对象处理复杂结构
• 不会使用单元测试特定代码（如Equals污染您的类型

缺点

• 只考虑可序列化的公共成员（不需要注释您的成员）
• 不处理循环引用

Answer 3

您应该提供Object.Equals和Object.GetHashCode的override ：

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();
}

至于检查两个集合是否相等，请使用Enumerable.SequenceEqual ：

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

请注意，您可能需要使用接受IEqualityComparer<T>的重载 。

Answer 4

看起来很喜欢AutoFixture的Likeness就是我对这个问题所需要的（感谢Mark Seeman）但是它并不支持比较收集元素的相似性（在这个问题上有几个未解决的问题，但它们尚未解决）。

我发现Kellerman Software的 CompareObjects可以解决问题：

https://github.com/GregFinzer/Compare-Net-Objects

Answer 5

这是我们用于比较复杂图形的NUnit 2.4.6自定义约束。 它支持嵌入式集合，父级引用，为数字比较设置容差，识别要忽略的字段名称（甚至在层次结构中的深层），以及始终忽略的装饰类型。

我确信这段代码可以在NUnit之外使用，大部分代码都不依赖于NUnit。

我们在成千上万的单元测试中使用它。

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 6

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

这篇文章可能很有用，我只是使用refcetion dump解决了这个问题; 然后我们只需要比较两个字符串。

代码在这里：

 /// <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;
        }
    }

Answer 7

我已经做了：

Assert.AreEqual(Newtonsoft.Json.JsonConvert.SerializeObject(object1),
                Newtonsoft.Json.JsonConvert.SerializeObject(object2));

Answer 8

Mark Seeman的答案涵盖了一般性问题：测试相等性是一个单独的问题，因此代码应该是类本身的外部。 （我之前没有见过“平等污染”，但那）。 此外，这是一个与您单元测试项目隔离的问题。 更好的是，在许多情况下它是一个“已解决的问题”：有许多可用的断言库允许您以任意数量的任意方式测试相等性。 他提出了一个问题，尽管有许多问题在这些年间如雨后春笋般涌现或变得更加成熟。

为此，我建议Fluent断言 。 它具有许多用于各种比较的功能。 在这种情况下，它将非常简单：

st1.ShouldBeEquivalentTo(st2); // before 5.0

要么

st1.Should().BeEquivalentTo(st2); // 5.0 and later

Answer 9

1. 您好首先将您的测试项目Newtonsoft.Json与Nuget PM一起添加

   PM> Install-Package Newtonsoft.Json -Version 10.0.3

2. 然后添加测试文件

    using Newtonsoft.Json; 

3. 用法：

    Assert.AreEqual( JsonConvert.SerializeObject(expected), JsonConvert.SerializeObject(actual)); 

Answer 10

您还可以使用具有此语法的NFluent深入比较两个对象，而不实现对象的相等性。 NFluent是一个试图简化可读测试代码编写的库。

Check.That(actual).HasFieldsWithSameValues(expected);

此方法失败，异常包含所有差异，而不是在第一个失败。 我发现这个功能是一个加号。

Answer 11

看看以下链接。 它是代码项目的解决方案，我也使用过它。 它适用于比较NUnit和MSUnit中的对象

http://www.codeproject.com/Articles/22709/Testing-Equality-of-Two-Objects?msg=5189539#xx5189539xx

Answer 12

也许你需要在类中添加一个public bool Equals(object o) 。

Answer 13

这就是我做的：

public static void AreEqualXYZ_UsageExample()
{
    AreEqualXYZ(actual: class1UnderTest, 
        expectedBoolExample: true, 
        class2Assert: class2 => Assert.IsNotNull(class2), 
        class3Assert: class3 => Assert.AreEqual(42, class3.AnswerToEverything));
}

public static void AreEqualXYZ(Class1 actual,
    bool expectedBoolExample,
    Action<Class2> class2Assert,
    Action<Class3> class3Assert)
{
    Assert.AreEqual(actual.BoolExample, expectedBoolExample);

    class2Assert(actual.Class2Property);
    class3Assert(actual.Class3Property);
}

HTH ..

Answer 14

如果您使用NUnit，您可以使用此语法并专门为测试指定IEqualityComparer ：

[Test]
public void CompareObjectsTest()
{
    ClassType object1 = ...;
    ClassType object2 = ...;
    Assert.That( object1, Is.EqualTo( object2 ).Using( new MyComparer() ) );
}

private class MyComparer : IEqualityComparer<ClassType>
{
    public bool Equals( ClassType x, ClassType y )
    {
        return ....
    }

    public int GetHashCode( ClassType obj )
    {
        return obj.GetHashCode();
    }
}

另请参见： 等约束（NUnit 2.4 / 2.5）

Answer 15

obj1.ToString().Equals(obj2.ToString())