NSubstitute ILogger .NET Core [英] NSubstitute ILogger .NET Core

问题描述

我正在尝试围绕异常处理编写单元测试，以便可以验证记录器是否正确记录了异常.我正在使用NSubstitute作为模拟框架，并且必须遵循Microsoft.Extensions.Logging.ILogger进行测试:

I am trying to write unit tests around my exception handling so that I can verify the my logger is properly logging the exception. I am using NSubstitute as a mocking framework and Microsoft.Extensions.Logging.ILogger I have to following for my test:

[Fact]
public void LogsExcpetionWhenErrorOccursInCreate()
{
   var newUser = new UserDataModel
   {
      FirstName = "Rick",
      MiddleName = "Jason",
      LastName = "Grimes",
      Email = "[e-mail]",
      Created = new DateTime(2007, 8, 15)
   };
   var exception = new Exception("Test Exception");
   // configure InsertOne to throw a generic excpetion
   _mongoContext.InsertOne(newUser).Returns(x => { throw exception; });

   try
   {
      _collection.Create(newUser);
   }
   catch
   {
      // validate that the logger logs the exception as an error
      _logger.Received().LogError(exception.Message);
   }
}

通过以下方法测试日志记录:

to test the logging in the following method:

public UserDataModel Create(UserDataModel user)
{
     try
     {
          return MongoContext.InsertOne(user);                
     }
     catch(Exception e)
     {
           _logger?.LogError(e.Message);
           throw new DataAccessException("An error occurred while attempting to create a user.", e);
      }

}

我的测试失败，并出现以下错误:

My test fails with the following error:

Message: NSubstitute.Exceptions.ReceivedCallsException : Expected to receive a call matching:
    Log<Object>(Error, 0, Test Exception, <null>, Func<Object, Exception, String>)
Actually received no matching calls.
Received 1 non-matching call (non-matching arguments indicated with '*' characters):
    Log<Object>(Error, 0, *Test Exception*, <null>, Func<Object, Exception, String>)

我不确定为什么会失败，因为即使在错误消息中，调用也一样.

I'm not sure why this is failing because even in then error message the calls are the same.

提前谢谢！

更新:

这里是测试的构造函数，这是我在其中插入记录器模拟程序的地方:

Here is the constructor for the test, this is where I am injecting the logger mock:

public UserCollectionTest()
{
   _mongoContext = Substitute.For<IMongoContext<UserDataModel>>();
   _logger = Substitute.For<ILogger>();
   // create UserCollection with our mock client
   _collection = new UserCollection(_mongoContext, _logger);
}

推荐答案

LogError不是ILogger方法，因此当您尝试检查是否已使用某些参数调用此方法时，NSubstitute会尝试以某种方式处理它(我不知道如何完全)并失败.

LogError is not a ILogger method, so when you try to check that this method was called with certain parameters NSubstitute tries to handle it somehow(I do not know how exactly) and fails.

LogError扩展方法的代码为:

The code of LogError extension method is:

public static void LogError(this ILogger logger, string message, params object[] args)
{
  if (logger == null)
    throw new ArgumentNullException("logger");
  logger.Log<object>(LogLevel.Error, (EventId) 0, (object) new FormattedLogValues(message, args), (Exception) null, LoggerExtensions._messageFormatter);
}

因此，您必须检查是否调用了Log方法.

So you have to check that Log method was called.

我简化了您的示例.我认为主意应该很清楚.

I simplified your example a bit. I think idea should be clear.

public partial class MainWindow : Window
{
    public MainWindow()
    {
        InitializeComponent();

        var logger = Substitute.For<ILogger>();
        try
        {
            Create(logger);
        }
        catch
        {
            logger.CheckErrorMessage("My Message");
        }
    }

    public string Create(ILogger logger)
    {
        try
        {
            throw new Exception("My Message");
        }
        catch (Exception e)
        {
            logger?.LogError(e.Message);
            throw new Exception("An error occurred while attempting to create a user.", e);
        }
    }
}

public static class TestExtensions
{
    public static void CheckErrorMessage(this ILogger logger, string message)
    {
        logger.Received().Log(
            LogLevel.Error,
            Arg.Any<EventId>(),
            Arg.Is<object>(o => o.ToString() == message),
            null,
            Arg.Any<Func<object, Exception, string>>());
    }
}

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