我试图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正确记录异常.我使用NSubstitute作为模拟框架和Microsoft.Extensions.Logging.ILogger我必须遵循我的测试：

[Fact]
public void LogsExcpetionWhenErrorOccursInCreate()
{
   var newUser = new UserDataModel
   {
      FirstName = "Rick",
      MiddleName = "Jason",
      LastName = "Grimes",
      Email = "rick.grimes@thedead.com",
      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记录：

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,出现以下错误：

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>)

我不确定为什么这会失败,因为即使在错误消息中,调用也是一样的.

提前致谢！

更新：

这是测试的构造函数,这是我注入logger mock的地方：

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

解决方法:

LogError不是ILogger方法,因此当您尝试检查此方法是否使用某些参数调用时,NSubstitute会尝试以某种方式处理它(我不知道具体如何)并失败.

LogError扩展方法的代码是：

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,您必须检查是否已调用Log方法.

我简化了你的例子.我认为这个想法应该是明确的.

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>>());
    }
}