Mocking HttpClient in .Net core 3 with Moq

I worked with HttpClient today and needed to write some unit tests. Here is how I did it. First off, we need to define an HttpClientFactory interface like this:

    public interface IHttpClientFactory
    {
        HttpClient CreateHttpClient();
    }

Your API code must then not directly create an http client, but pass in a IHttpClientFactory instance, allowing for tailored functionality such as mocking / unit testing. A default implementation could be:

  public class DefaultHttpClientFactory : IHttpClientFactory
        {
            public HttpClient CreateHttpClient()
            {
                return new HttpClient();
            }
        }

And a mock implementation using Moq then looks like this:

using Moq;
using Moq.Protected;
using System.Net;
using System.Net.Http;
using System.Threading;
using System.Threading.Tasks;

namespace SomeAcme.SomeApi.Test
{
    public class MockHttpClientFactory : IHttpClientFactory
    {
        private HttpResponseMessage _httpContentMessage;

        public HttpClient CreateHttpClient()
        {
            return new HttpClient(CreateMockedHttpMessageHandler());
        }

        private HttpMessageHandler CreateMockedHttpMessageHandler()
        {
            var handlerMock = new Mock<HttpMessageHandler>(MockBehavior.Strict);
            handlerMock
                .Protected()
                // Setup the PROTECTED method to mock
                .Setup<Task<HttpResponseMessage>>(
                    "SendAsync",
                    ItExpr.IsAny<HttpRequestMessage>(),
                    ItExpr.IsAny<CancellationToken>()
                )
                // prepare the expected response of the mocked http call
                .ReturnsAsync(SetupHttpResponseMessage())
                .Verifiable();

            handlerMock
                .Protected()
                // Setup the PROTECTED method to mock
                .Setup(
                    "Dispose",
                    ItExpr.IsAny<bool>()
                )
                // prepare the expected response of the mocked http call
                .Verifiable();
            return handlerMock.Object;
        }

        /// <summary>
        /// Set up the desired http response of unit tests
        /// </summary>
        /// <param name="statusCode"></param>
        /// <param name="responseJson"></param>
        public void SetHttpResponseMessage(HttpStatusCode statusCode, string responseJson)
        {
            _httpContentMessage = new HttpResponseMessage
            {
                StatusCode = statusCode,
                Content = new StringContent(responseJson)

            };

        }

        private HttpResponseMessage SetupHttpResponseMessage()
        {
            if (_httpContentMessage != null)
                return _httpContentMessage;
            return new HttpResponseMessage()
            {
                StatusCode = HttpStatusCode.OK,
                Content = new StringContent("[{'id':1,'value':'1'}]")
            }; //return default dummy implementation for easy green testing of HttpClient..
        }
    }
}

The key is to implement a mocked HttpMessageHandler which is then injected into the real HttpClient class. And also expose a method SetupHttpResponseMessage() allowing unit tests to specify desired http status code and json payload in the response. This is a very basic approach of unit testing HttpClient, so you can get code coverage of your HttpClient and related code in the application layer where your use it. Make sure you now inject the MockHttpClientFactory into your code and initialize it in your testse setting the SetupHttpResponseMessage. Tests should go a green again despite you actually use the HttpClient (with a mocked HttpMessageHandler) !

User friendly and Flexible numeric textbox for decimal numbers in WPF

Adapting WPF to allow a numeric textbox in WPF sounds very trivial, but it is not! A user friendly textbox in WPF couldhave different aspects. It could be possible to: - Only allow numbers or decimal separator - Possible to specify number of digits for integer part and number of digits for decimal part - Specify an empty default value - Still rely on default components such as WPF Textbox The following WPF Converter allows to restrict user input using ConvertBack method. Usually a developer implements the Convert method to transform output, here we use ConvertBack to filter input to only allow numbers or decimal separator.

NumericFormatConverter

using Hemit.OpPlan.Common;
using System;
using System.Globalization;
using System.Linq;
using System.Threading;
using System.Windows.Data;
namespace Hemit.OpPlan.Client.Infrastructure.Converters
{
    public class NumericFormatConverter : IValueConverter
    {
        public int IntegerLength { get; set; }
        public int DecimalLength { get; set; }
        public string DefaultValue { get; set; }
        public object Convert(object value, Type targetType, object parameter, CultureInfo culture)
        {
            return value;       
        }
        public object ConvertBack(object value, Type targetType, object parameter, CultureInfo culture)
        {
            if (value == null)
                return DefaultValue;
            string adjustedValue = AdjustValueToAcceptingFormat(value.ToString());
            return adjustedValue;
        }
        private string AdjustValueToAcceptingFormat(string value)
        {
            if (string.IsNullOrEmpty(value))
                return DefaultValue;
            char decimalSeparator = Thread.CurrentThread?.CurrentCulture?.NumberFormat?.NumberDecimalSeparator.ToCharArray().First() ?? ',';
            string[] compounds = value.Split(new[] { decimalSeparator });
            if (compounds.Length <= 0)
            {
                return DefaultValue; //default to zero
            }
            if (compounds.Length == 1)
            {
                return NumericDigits(compounds[0], decimalSeparator);
            }
            return $"{NumericDigits(compounds[0], decimalSeparator).Truncate(3)}{decimalSeparator}{NumericDigits(compounds[1], decimalSeparator).Truncate(1)}";
        }
        private static string NumericDigits(string input, char decimalSeparator)
        {
            return string.Join("", input.ToCharArray().Where(ch => Char.IsDigit(ch) || ch == decimalSeparator)).Truncate(3);
        }
    }
}

If you rely on MVVM, you can bind up a numeric value with a proxy property with datatype string for flexible input.

   [State]
   [NotifyPropertyChanged(true)]
   [AffectsOtherProperty("BodyMassIndex")]
   [Range(0.0, 500, ErrorMessage = @"Max Weight is surpassed")]
   public double? Weight { get; set; }

   private string _weightInputValue;

   public string WeightInputValue
   {
       get { return _weightInputValue; }
       set
       {
           if (_weightInputValue != value)
           {
               _weightInputValue = value;
               double weight;
               if (double.TryParse(_weightInputValue, out weight))
               {
                   Weight = weight;
               }
               RaisePropertyChanged(() => WeightInputValue);
           }
       }
   }

Never mind the Postsharp aspects for State, NotifyPropertyChanged and AffectsOtherProperty listed here, they are not necessary in your use case. But shows a real world scenario. In WPF frontend you can then bind up the WPF converter like this:

      <TextBlock Grid.Row="7" Grid.Column="2" Margin="2" Text="Vekt (kg)" VerticalAlignment="Center" HorizontalAlignment="Left" />
                            <TextBox Grid.Row="7" Grid.Column="4" MaxLength="5" Height="24" behaviors:TextBoxRegExBehavior.RegularExpressionProperty="^\d+[,|.]*\d*$" FontWeight="Normal"
                             HorizontalAlignment="Left"
                             behaviors:TextBoxRegExBehavior.MaxLength="5" behaviors:TextBoxRegExBehavior.MustParseToType="{x:Type sys:Double}" behaviors:TextBoxRegExBehavior.EmptyValue="0" 
                             Margin="2,2,2,2" Width="40" Text="{Binding WeightInputValue, Converter={StaticResource numericFormatConverter}, ConverterCulture={x:Static gl:CultureInfo.CurrentCulture}, UpdateSourceTrigger=PropertyChanged, ValidatesOnExceptions=true}" 
                             Style="{StaticResource ReadOnlyTextBoxStyleHidingZero}" IsReadOnly="{Binding IsEditMode, Converter={StaticResource invertedBoolConverter}}" TabIndex="35" />

Again, much custom stuff here, but the key thing to notice is that you only need to make sure you bind against the proxy property of type string, the WPF converter numericFormatConverter handles the formatting of the input.

   <converters:NumericFormatConverter x:Key="numericFormatConverter" IntegerLength="3" DecimalLength="1" DefaultValue=""></converters:NumericFormatConverter>

Strongly typed ConfigurationManager in .NET Framework

Handling configuration files in .NET Framework is often tedious. You retrieve the app setting as a string and must then parse it out. Dont you wish we could have a generic method to get a strongly typed app setting instead and spare ourselves with some code ? Sure you can!

using System;
using System.ComponentModel;
using System.Configuration;

namespace Hemit.OpPlan.Common.Extensions
{

    /// <summary>
    /// Utility methods for ConfigurationManager. Also included methods for handling OpenExeConfiguration (running process configuration, for example in tests and installers)
    /// </summary>
    public static class ConfigurationManagerWrapper
    {
        /// <summary>
        /// Sets an appsetting for the exe configuration
        /// </summary>
        /// <param name="appsetting"></param>
        /// <param name="value"></param>
        public static void SetAppsettingForExecConfiguration(string appsetting, object value)
        {
            System.Configuration.Configuration config = ConfigurationManager.OpenExeConfiguration(ConfigurationUserLevel.None);
            config.AppSettings.Settings[appsetting].Value = Convert.ToString(value);
            config.Save(ConfigurationSaveMode.Modified);
        }

        /// <summary>
        /// Sets an appsetting for the exe configuration
        /// </summary>
        /// <param name="appsetting"></param>
        /// <param name="value"></param>
        public static string GetAppsettingExecConfiguration(string appsetting, object value)
        {
            return ConfigurationManager.AppSettings[appsetting];
        }

        /// <summary>
        /// Sets an appsetting for the exe configuration
        /// </summary>
        /// <param name="appsetting"></param>
        /// <param name="value"></param>
        public static void SetAppsettingForConfiguration(string appsetting, object value)
        {
            ConfigurationManager.AppSettings[appsetting] = Convert.ToString(value);
        }

        /// <summary>
        /// Sets an appsetting for the exe configuration
        /// </summary>
        /// <param name="appsetting"></param>
        /// <param name="value"></param>
        public static string GetAppsettingForExecConfiguration(string appsetting, object value)
        {
            System.Configuration.Configuration config = ConfigurationManager.OpenExeConfiguration(ConfigurationUserLevel.None);
            return config.AppSettings.Settings[appsetting].Value;
        }


        /// <summary>
        /// Use this extension method to get a strongly typed app setting from the configuration file.
        /// Returns app setting in configuration file if key found and tries to convert the value to a specified type. In case this fails, the fallback value
        /// or if NOT specified - default value - of the app setting is returned
        /// </summary>
        /// <typeparam name="T"></typeparam>
        /// <param name="appsettingKey"></param>
        /// <param name="fallback"></param>
        /// <returns></returns>
        public static T GetAppsetting<T>(string appsettingKey, T fallback = default(T))
        {
            string val = ConfigurationManager.AppSettings[appsettingKey] ?? "";
            if (!string.IsNullOrEmpty(val))
            {
                try
                {
                    Type typeDefault = typeof(T);
                    var converter = TypeDescriptor.GetConverter(typeof(T));
                    return converter.CanConvertFrom(typeof(string)) ? (T)converter.ConvertFrom(val) : fallback;
                }
                catch (Exception err)
                {
                    Console.WriteLine(err); //Swallow exception
                    return fallback;
                }
            }
            return fallback;
        }

    }
}