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

问题描述

我正在尝试围绕我的异常处理编写单元测试，以便我可以验证我的记录器是否正确记录了异常.我使用 NSubstitute 作为模拟框架，并且 Microsoft.Extensions.Logging.ILogger 我必须按照以下步骤进行测试:

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);
   }
}

使用以下方法测试日志:

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是相同的.

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

提前致谢！

更新:

这是测试的构造函数，这是我注入记录器模拟的地方:

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使用某些参数调用此方法时，NSubstitute 尝试以某种方式处理它(我不知道如何完全正确)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.

我稍微简化了您的示例.我觉得思路应该很清楚.

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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