NSubstitute ILogger .NET核

Question

我试图围绕异常处理编写单元测试，以便验证我的记录器是否正确地记录了异常。我正在使用NSubstitute作为一个模拟框架，在测试中必须遵循Microsoft.Extensions.Logging.ILogger：

[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);
   }
}

要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，有以下错误：

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>)

我不知道为什么会失败，因为即使在错误消息中，调用也是相同的。

提前感谢！

更新：

下面是测试的构造函数，这就是我要注入记录器模拟的地方：

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

Answer 1

LogError不是一个ILogger方法，所以当您尝试用某些参数调用该方法时，NSubstitute尝试以某种方式处理它(我不知道具体情况)，并失败了。

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，您必须检查日志方法是否被调用。

我把你的例子简化了一点。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>>());
    }
}

Answer 2

看起来，接受的答案在.NET核心3或.NET 5中不起作用。

下面是在github问题中找到的解决办法

创建一个新的MockLogger类

public abstract class MockLogger : ILogger
{
    void ILogger.Log<TState>(LogLevel logLevel, EventId eventId, TState state, Exception exception, Func<TState, Exception, string> formatter) => 
        Log(logLevel, formatter(state, exception));

    public abstract void Log(LogLevel logLevel, string message);

    public virtual bool IsEnabled(LogLevel logLevel) => true;

    public abstract IDisposable BeginScope<TState>(TState state);
}

用新的模拟记录器替换您的模拟记录器。

// Old 
// var logger = Substitute.For<ILogger>();
// New
var logger = Substitute.For<MockLogger>();

使用新的记录器检查调用

logger.Received().Log(LogLevel.Error, Arg.Is<string>(s => s.Contains("some log message")));

要与泛型ILogger<T>一起使用，只需将类更改为

public abstract class MockLogger<T> : ILogger<T>

Answer 3

这是我的方法，正在进一步发展。并扩展了Githhub问题。

第一个记录器：

using Microsoft.Extensions.Logging;

public abstract class MockLogger<T> : ILogger<T>
{
    void ILogger.Log<TState>(LogLevel logLevel, EventId eventId, TState state, Exception? exception, Func<TState, Exception?, string> formatter)
    {
        var unboxed = (IReadOnlyList<KeyValuePair<string, object>>)state!;
        string message = formatter(state, exception);

        this.Log();
        this.Log(logLevel, message, exception);
        this.Log(logLevel, unboxed.ToDictionary(k => k.Key, v => v.Value), exception);
    }

    public abstract void Log();

    public abstract void Log(LogLevel logLevel, string message, Exception? exception = null);

    public abstract void Log(LogLevel logLevel, IDictionary<string, object> state, Exception? exception = null);

    public virtual bool IsEnabled(LogLevel logLevel)
    {
        return true;
    }

    public abstract IDisposable BeginScope<TState>(TState state);
}

现在使用：

MockLogger<Service> logger = Substitute.For<MockLogger<Service>>();
logger.IsEnabled(LogLevel.Error).Returns(true);

string originalFormat = "Service returned error with code: '{statusCode}' and reason: '{reason}'";
var statusCode = HttpStatusCode.BadRequest;
string reason = "The reason...";

string message = $"Service returned error with code: '{(int)statusCode}' and reason: '{reason}'";

// Assert
logger.Received(1).Log(
            LogLevel.Error,
            Arg.Is<IDictionary<string, object>>(
                dict =>
                    dict.Any(kv => kv.Key == "{OriginalFormat}" && (string)kv.Value == originalFormat) &&
                    dict.Any(kv => kv.Key == "statusCode" && (int)kv.Value == (int)statusCode) &&
                    dict.Any(kv => kv.Key == "reason" && (string)kv.Value == reason)));

logger.Received(1).Log(LogLevel.Error, message);
logger.Received(1).Log();

它允许单独测试日志参数。