Object verifier for SpecFlow

SpecFlow.ObjectVerifier.cs

using System;
using System.Collections.Generic;
using System.ComponentModel;
using System.Linq.Expressions;

namespace TechTalk.SpecFlow.ObjectVerification
{
    public static class ObjectVerifierExtensions
    {
        /// <summary>
        /// Specifies the aliases in the verification data for the given property of the object. There can be more than one alias for any property, but not vice versa.
        /// </summary>
        public static IConfiguredObjectVerifier<TObject> WithPropertyAlias<TObject, TProperty>(this IConfiguredObjectVerifier<TObject> objectVerifier, Expression<Func<TObject, TProperty>> selector, params string[] aliases)
        {
            foreach (var alias in aliases)
                objectVerifier.WithPropertyAlias(selector, alias);
            return objectVerifier;
        }

        /// <summary>
        /// Specifies the equality comparer to use when verifying the given field mapped to the verified object (comparison priority: table field, object property, target value, default)
        /// </summary>
        public static IConfiguredObjectVerifier<TObject> WithFieldEqualityComparer<TObject, TValue>(this IConfiguredObjectVerifier<TObject> objectVerifier, string name, IEqualityComparer<TValue> comparer)
        {
            objectVerifier.WithFieldEqualityComparer<TValue>(name, (a, b) => comparer.Equals(a, b));
            return objectVerifier;
        }

        /// <summary>
        /// Specifies the equality comparer to use when verifying the given property of the verified object (comparison priority: table field, object property, target value, default)
        /// </summary>
        public static IConfiguredObjectVerifier<TObject> WithPropertyEqualityComparer<TObject, TValue>(this IConfiguredObjectVerifier<TObject> objectVerifier, Expression<Func<TObject, TValue>> selector, IEqualityComparer<TValue> comparer)
        {
            objectVerifier.WithPropertyEqualityComparer<TValue>(selector, (a, b) => comparer.Equals(a, b));
            return objectVerifier;
        }

        /// <summary>
        /// Specifies the equality comparer to use when verifying properties of the given type (comparison priority: table field, object property, target value, default)
        /// </summary>
        public static IConfiguredObjectVerifier<TObject> WithTypeEqualityComparer<TObject, TValue>(this IConfiguredObjectVerifier<TObject> objectVerifier, IEqualityComparer<TValue> comparer)
        {
            objectVerifier.WithTypeEqualityComparer<TValue>((a, b) => comparer.Equals(a, b));
            return objectVerifier;
        }

        /// <summary>
        /// Returns a converter function for the given type. This method is the default converter provider.
        /// </summary>
        public static Func<string, object> GetDefaultConverter(Type type)
        {
            if (type == typeof(string))
                return s => s;

            if (type.IsGenericType && type.Name == "Nullable`1")
                return val =>
                {
                    if (string.IsNullOrEmpty(val)) return null;
                    else return GetDefaultConverter(type.GetGenericArguments()[0])(val);
                };

            if (type.IsEnum)
                return value => Enum.Parse(type, value);

            return value => TypeDescriptor.GetConverter(type).ConvertFromString(value);
        }
    }

    public static class ExpressionExtensions
    {
        /// <summary>
        /// Returns the property name from a property selector expression
        /// </summary>
        public static string GetPropertyName<TObject, TValue>(this Expression<Func<TObject, TValue>> property)
        {
            var exp = (LambdaExpression)property;

            if (exp.Body.NodeType == ExpressionType.Parameter)
                return "item";

            var mExp = (exp.Body.NodeType == ExpressionType.MemberAccess) ?
                (MemberExpression)exp.Body :
                (MemberExpression)((UnaryExpression)exp.Body).Operand;
            return mExp.Member.Name;
        }
    }

    public interface IObjectVerifier<TObject>
    {
        /// <summary>
        /// Allows customizing the object verification
        /// </summary>
        IConfiguredObjectVerifier<TObject> WithConfiguration();

        /// <summary>
        /// Verifies the object with a vertical property-value collection
        /// </summary>
        string[] Verify(IEnumerable<IDictionary<string, string>> expected, TObject actual);
    }

    public interface IConfiguredObjectVerifier<TObject> : IObjectVerifier<TObject>
    {
        /// <summary>
        /// Specifies an alias in the verification data for the given property of the object. There can be more than one alias for any property, but not vice versa.
        /// </summary>
        IConfiguredObjectVerifier<TObject> WithPropertyAlias<TProperty>(Expression<Func<TObject, TProperty>> selector, string alias);

        /// <summary>
        /// Specifies the converter to use for the given verification data field (converter priority: table field, object property, target value, default)
        /// </summary>
        IConfiguredObjectVerifier<TObject> WithFieldValueConverter<TProperty>(string name, Func<string, TProperty> converter);
        /// <summary>
        /// Specifies the converter to use for the given property of the verified object (converter priority: table field, object property, target value, default)
        /// </summary>
        IConfiguredObjectVerifier<TObject> WithPropertyValueConverter<TProperty>(Expression<Func<TObject, TProperty>> selector, Func<string, TProperty> converter);
        /// <summary>
        /// Specifies a conversion method to use when converting to the given value (converter priority: table field, object property, target value, default)
        /// </summary>
        IConfiguredObjectVerifier<TObject> WithTypeValueConverter<TValue>(Func<string, TValue> converter);
        /// <summary>
        /// Specifies the provider method to use to obtain the default value converter for any given type (converter priority: table field, object property, target value, default)
        /// </summary>
        IConfiguredObjectVerifier<TObject> WithDefaultConverter(Func<Type, Func<string, object>> converterProvider);

        /// <summary>
        /// Specifies the equality comparison method to use when verifying the given field mapped to the verified object (comparison priority: table field, object property, target value, default)
        /// </summary>
        IConfiguredObjectVerifier<TObject> WithFieldEqualityComparer<TValue>(string name, Func<TValue, TValue, bool> comparer);
        /// <summary>
        /// Specifies the equality comparison method to use when verifying the given property of the verified object (comparison priority: table field, object property, target value, default)
        /// </summary>
        IConfiguredObjectVerifier<TObject> WithPropertyEqualityComparer<TValue>(Expression<Func<TObject, TValue>> selector, Func<TValue, TValue, bool> comparer);
        /// <summary>
        /// Specifies the equality comparison method to use when verifying properties of the given type (comparison priority: table field, object property, target value, default)
        /// </summary>
        IConfiguredObjectVerifier<TObject> WithTypeEqualityComparer<TValue>(Func<TValue, TValue, bool> comparer);
    }

    public static class ObjectVerifier
    {
        /// <summary>
        /// Creates an object verifier for a vertical property-value collection with the specified field keys.
        /// </summary>
        /// <param name="keyField">field for property names</param>
        /// <param name="valueField">field for property values</param>
        public static IObjectVerifier<TObject> For<TObject>(string keyField, string valueField)
        {
            return new ObjectVerifier<TObject>(keyField, valueField);
        }
    }

    internal sealed class ObjectVerifier<TObject> : IConfiguredObjectVerifier<TObject>
    {
        private readonly string keyField;
        private readonly string valueField;
        internal ObjectVerifier(string keyField, string valueField)
        {
            this.keyField = keyField;
            this.valueField = valueField;
        }

        public string[] Verify(IEnumerable<IDictionary<string, string>> expectedObject, TObject actualObject)
        {
            var errors = new List<string>();
            foreach (var item in expectedObject)
            {
                var fieldName = item[keyField];
                var propertyName = fieldName;
                if (propertyAliases.ContainsKey(propertyName))
                    propertyName = propertyAliases[propertyName];

                var property = typeof(TObject).GetProperty(propertyName);
                if (property == null)
                    throw new InvalidOperationException(string.Format("Invalid property name '{0}'", propertyName));

                Func<string, object> converter = null;
                if (converter == null) fieldValueConverters.TryGetValue(fieldName, out converter);
                if (converter == null) propertyValueConverters.TryGetValue(propertyName, out converter);
                if (converter == null) valueConverters.TryGetValue(property.PropertyType, out converter);
                if (converter == null) converter = defaultConverterProvider(property.PropertyType);

                Func<object, object, bool> comparer = null;
                if (comparer == null) fieldComparers.TryGetValue(fieldName, out comparer);
                if (comparer == null) propertyComparers.TryGetValue(propertyName, out comparer);
                if (comparer == null) equalityComparers.TryGetValue(property.PropertyType, out comparer);
                if (comparer == null) comparer = (exp, act) => object.Equals(exp, act);

                var expectedValue = converter(item[valueField]);
                var actualValue = property.GetValue(actualObject);
                if (!comparer(expectedValue, actualValue))
                    errors.Add(string.Format("The values for {0} do not match (expected:<{2}>, actual:<{3}>)",
                        fieldName, propertyName, expectedValue, actualValue));
            }
            return errors.ToArray();
        }

        public IConfiguredObjectVerifier<TObject> WithConfiguration()
        {
            return this;
        }

        private Func<Type, Func<string, object>> defaultConverterProvider = ObjectVerifierExtensions.GetDefaultConverter;
        public IConfiguredObjectVerifier<TObject> WithDefaultConverter(Func<Type, Func<string, object>> converterProvider)
        {
            defaultConverterProvider = converterProvider;
            return this;
        }

        private readonly Dictionary<string, string> propertyAliases = new Dictionary<string, string>();
        public IConfiguredObjectVerifier<TObject> WithPropertyAlias<TProperty>(Expression<Func<TObject, TProperty>> selector, string alias)
        {
            propertyAliases.Add(alias, selector.GetPropertyName());
            return this;
        }

        private readonly Dictionary<string, Func<string, object>> fieldValueConverters = new Dictionary<string, Func<string, object>>();
        public IConfiguredObjectVerifier<TObject> WithFieldValueConverter<TProperty>(string name, Func<string, TProperty> converter)
        {
            fieldValueConverters.Add(name, v => converter(v));
            return this;
        }

        private readonly Dictionary<string, Func<string, object>> propertyValueConverters = new Dictionary<string, Func<string, object>>();
        public IConfiguredObjectVerifier<TObject> WithPropertyValueConverter<TProperty>(Expression<Func<TObject, TProperty>> selector, Func<string, TProperty> converter)
        {
            propertyValueConverters.Add(selector.GetPropertyName(), v => converter(v));
            return this;
        }

        private readonly Dictionary<Type, Func<string, object>> valueConverters = new Dictionary<Type, Func<string, object>>();
        public IConfiguredObjectVerifier<TObject> WithTypeValueConverter<TValue>(Func<string, TValue> converter)
        {
            valueConverters.Add(typeof(TValue), v => converter(v));
            return this;
        }

        private readonly Dictionary<string, Func<object, object, bool>> fieldComparers = new Dictionary<string, Func<object, object, bool>>();
        public IConfiguredObjectVerifier<TObject> WithFieldEqualityComparer<TValue>(string name, Func<TValue, TValue, bool> comparer)
        {
            fieldComparers.Add(name, (a, b) => comparer((TValue)a, (TValue)b));
            return this;
        }

        private readonly Dictionary<string, Func<object, object, bool>> propertyComparers = new Dictionary<string, Func<object, object, bool>>();
        public IConfiguredObjectVerifier<TObject> WithPropertyEqualityComparer<TValue>(Expression<Func<TObject, TValue>> selector, Func<TValue, TValue, bool> comparer)
        {
            propertyComparers.Add(selector.GetPropertyName(), (a, b) => comparer((TValue)a, (TValue)b));
            return this;
        }

        private readonly Dictionary<Type, Func<object, object, bool>> equalityComparers = new Dictionary<Type, Func<object, object, bool>>();
        public IConfiguredObjectVerifier<TObject> WithTypeEqualityComparer<TValue>(Func<TValue, TValue, bool> comparer)
        {
            equalityComparers.Add(typeof(TValue), (a, b) => comparer((TValue)a, (TValue)b));
            return this;
        }
    }
}