c# - 如何在 ASP.NET Core 中使用 ILogger 进行单元测试

Question

这是我的控制器：

public class BlogController : Controller
{
    private IDAO<Blog> _blogDAO;
    private readonly ILogger<BlogController> _logger;

    public BlogController(ILogger<BlogController> logger, IDAO<Blog> blogDAO)
    {
        this._blogDAO = blogDAO;
        this._logger = logger;
    }
    public IActionResult Index()
    {
        var blogs = this._blogDAO.GetMany();
        this._logger.LogInformation("Index page say hello", new object[0]);
        return View(blogs);
    }
}

如您所见，我有 2 个依赖项， aIDAO和 aILogger

这是我的测试类，我使用 xUnit 进行测试，使用 Moq 创建模拟和存根，我可以DAO轻松模拟，但是ILogger我不知道该怎么做，所以我只是传递 null 并注释掉登录控制器的调用运行测试时。有没有办法测试但仍然以某种方式保留记录器？

public class BlogControllerTest
{
    [Fact]
    public void Index_ReturnAViewResult_WithAListOfBlog()
    {
        var mockRepo = new Mock<IDAO<Blog>>();
        mockRepo.Setup(repo => repo.GetMany(null)).Returns(GetListBlog());
        var controller = new BlogController(null,mockRepo.Object);

        var result = controller.Index();

        var viewResult = Assert.IsType<ViewResult>(result);
        var model = Assert.IsAssignableFrom<IEnumerable<Blog>>(viewResult.ViewData.Model);
        Assert.Equal(2, model.Count());
    }
}

score 207 · Accepted Answer

只需模拟它以及任何其他依赖项：

var mock = new Mock<ILogger<BlogController>>();
ILogger<BlogController> logger = mock.Object;

//or use this short equivalent 
logger = Mock.Of<ILogger<BlogController>>()

var controller = new BlogController(logger);

您可能需要安装Microsoft.Extensions.Logging.Abstractions软件包才能使用ILogger<T>.

此外，您可以创建一个真正的记录器：

var serviceProvider = new ServiceCollection()
    .AddLogging()
    .BuildServiceProvider();

var factory = serviceProvider.GetService<ILoggerFactory>();

var logger = factory.CreateLogger<BlogController>();

score 132 · Accepted Answer

实际上，我发现Microsoft.Extensions.Logging.Abstractions.NullLogger<>这看起来是一个完美的解决方案。安装包Microsoft.Extensions.Logging.Abstractions，然后按照示例进行配置和使用：

using Microsoft.Extensions.Logging;

public void ConfigureServices(IServiceCollection services)
{
    ...

    services.AddSingleton<ILoggerFactory, NullLoggerFactory>();

    ...
}

using Microsoft.Extensions.Logging;

public class MyClass : IMyClass
{
    public const string ErrorMessageILoggerFactoryIsNull = "ILoggerFactory is null";

    private readonly ILogger<MyClass> logger;

    public MyClass(ILoggerFactory loggerFactory)
    {
        if (null == loggerFactory)
        {
            throw new ArgumentNullException(ErrorMessageILoggerFactoryIsNull, (Exception)null);
        }

        this.logger = loggerFactory.CreateLogger<MyClass>();
    }
}

和单元测试

//using Microsoft.VisualStudio.TestTools.UnitTesting;
//using Microsoft.Extensions.Logging;

[TestMethod]
public void SampleTest()
{
    ILoggerFactory doesntDoMuch = new Microsoft.Extensions.Logging.Abstractions.NullLoggerFactory();
    IMyClass testItem = new MyClass(doesntDoMuch);
    Assert.IsNotNull(testItem);
}

score 80 · Accepted Answer

更新（感谢@Gopal Krishnan 的评论）：

对于 Moq >= 4.15.0，以下代码可以正常工作（不再需要演员表）：

 loggerMock.Verify(
                x => x.Log(
                    LogLevel.Information,
                    It.IsAny<EventId>(),
                    It.Is<It.IsAnyType>((o, t) => string.Equals("Index page say hello", o.ToString(), StringComparison.InvariantCultureIgnoreCase)),
                    It.IsAny<Exception>(),
                    It.IsAny<Func<It.IsAnyType, Exception, string>>()),
                Times.Once);

以前版本的答案（对于 Moq < 4.15.0）：

对于使用 Moq 的 .net core 3 答案

由于 ILogger.Log 中的问题TState 中描述的更改而不再工作，以前是对象，现在是 FormattedLogValues

幸运的是stakx提供了一个很好的解决方法。所以我发布它是希望它可以为其他人节省时间（花了一段时间才弄清楚）：

 loggerMock.Verify(
                x => x.Log(
                    LogLevel.Information,
                    It.IsAny<EventId>(),
                    It.Is<It.IsAnyType>((o, t) => string.Equals("Index page say hello", o.ToString(), StringComparison.InvariantCultureIgnoreCase)),
                    It.IsAny<Exception>(),
                    (Func<It.IsAnyType, Exception, string>) It.IsAny<object>()),
                Times.Once);

score 44 · Accepted Answer

使用自定义记录器ITestOutputHelper（来自 xunit）来捕获输出和日志。以下是一个仅将写入state输出的小示例。

public class XunitLogger<T> : ILogger<T>, IDisposable
{
    private ITestOutputHelper _output;

    public XunitLogger(ITestOutputHelper output)
    {
        _output = output;
    }
    public void Log<TState>(LogLevel logLevel, EventId eventId, TState state, Exception exception, Func<TState, Exception, string> formatter)
    {
        _output.WriteLine(state.ToString());
    }

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

    public IDisposable BeginScope<TState>(TState state)
    {
        return this;
    }

    public void Dispose()
    {
    }
}

在你的单元测试中使用它，比如

public class BlogControllerTest
{
  private XunitLogger<BlogController> _logger;

  public BlogControllerTest(ITestOutputHelper output){
    _logger = new XunitLogger<BlogController>(output);
  }

  [Fact]
  public void Index_ReturnAViewResult_WithAListOfBlog()
  {
    var mockRepo = new Mock<IDAO<Blog>>();
    mockRepo.Setup(repo => repo.GetMany(null)).Returns(GetListBlog());
    var controller = new BlogController(_logger,mockRepo.Object);
    // rest
  }
}

score 17 · Accepted Answer

添加我的 2 美分，这是一个帮助扩展方法，通常放在静态帮助类中：

static class MockHelper
{
    public static ISetup<ILogger<T>> MockLog<T>(this Mock<ILogger<T>> logger, LogLevel level)
    {
        return logger.Setup(x => x.Log(level, It.IsAny<EventId>(), It.IsAny<object>(), It.IsAny<Exception>(), It.IsAny<Func<object, Exception, string>>()));
    }

    private static Expression<Action<ILogger<T>>> Verify<T>(LogLevel level)
    {
        return x => x.Log(level, 0, It.IsAny<object>(), It.IsAny<Exception>(), It.IsAny<Func<object, Exception, string>>());
    }

    public static void Verify<T>(this Mock<ILogger<T>> mock, LogLevel level, Times times)
    {
        mock.Verify(Verify<T>(level), times);
    }
}

然后，您可以像这样使用它：

//Arrange
var logger = new Mock<ILogger<YourClass>>();
logger.MockLog(LogLevel.Warning)

//Act

//Assert
logger.Verify(LogLevel.Warning, Times.Once());

当然，您可以轻松地扩展它来模拟任何期望（即期望、消息等……）

score 8 · Accepted Answer

在@ivan-samygin 和@stakx 的工作上更进一步，这里有一些扩展方法也可以匹配异常和所有日志值（KeyValuePairs）。

这些工作（在我的机器上；））与 .Net Core 3、Moq 4.13.0 和 Microsoft.Extensions.Logging.Abstractions 3.1.0 一起工作。

/// <summary>
/// Verifies that a Log call has been made, with the given LogLevel, Message and optional KeyValuePairs.
/// </summary>
/// <typeparam name="T">Type of the class for the logger.</typeparam>
/// <param name="loggerMock">The mocked logger class.</param>
/// <param name="expectedLogLevel">The LogLevel to verify.</param>
/// <param name="expectedMessage">The Message to verify.</param>
/// <param name="expectedValues">Zero or more KeyValuePairs to verify.</param>
public static void VerifyLog<T>(this Mock<ILogger<T>> loggerMock, LogLevel expectedLogLevel, string expectedMessage, params KeyValuePair<string, object>[] expectedValues)
{
    loggerMock.Verify(mock => mock.Log(
        expectedLogLevel,
        It.IsAny<EventId>(),
        It.Is<It.IsAnyType>((o, t) => MatchesLogValues(o, expectedMessage, expectedValues)),
        It.IsAny<Exception>(),
        It.IsAny<Func<object, Exception, string>>()
        )
    );
}

/// <summary>
/// Verifies that a Log call has been made, with LogLevel.Error, Message, given Exception and optional KeyValuePairs.
/// </summary>
/// <typeparam name="T">Type of the class for the logger.</typeparam>
/// <param name="loggerMock">The mocked logger class.</param>
/// <param name="expectedMessage">The Message to verify.</param>
/// <param name="expectedException">The Exception to verify.</param>
/// <param name="expectedValues">Zero or more KeyValuePairs to verify.</param>
public static void VerifyLog<T>(this Mock<ILogger<T>> loggerMock, string expectedMessage, Exception expectedException, params KeyValuePair<string, object>[] expectedValues)
{
    loggerMock.Verify(logger => logger.Log(
        LogLevel.Error,
        It.IsAny<EventId>(),
        It.Is<It.IsAnyType>((o, t) => MatchesLogValues(o, expectedMessage, expectedValues)),
        It.Is<Exception>(e => e == expectedException),
        It.Is<Func<It.IsAnyType, Exception, string>>((o, t) => true)
    ));
}

private static bool MatchesLogValues(object state, string expectedMessage, params KeyValuePair<string, object>[] expectedValues)
{
    const string messageKeyName = "{OriginalFormat}";

    var loggedValues = (IReadOnlyList<KeyValuePair<string, object>>)state;

    return loggedValues.Any(loggedValue => loggedValue.Key == messageKeyName && loggedValue.Value.ToString() == expectedMessage) &&
           expectedValues.All(expectedValue => loggedValues.Any(loggedValue => loggedValue.Key == expectedValue.Key && loggedValue.Value == expectedValue.Value));
}

score 8 · Accepted Answer

如果一个仍然是实际的。在 .net core >= 3 的测试中记录输出的简单方法

[Fact]
public void SomeTest()
{
    using var logFactory = LoggerFactory.Create(builder => builder.AddConsole());
    var logger = logFactory.CreateLogger<AccountController>();
    
    var controller = new SomeController(logger);

    var result = controller.SomeActionAsync(new Dto{ ... }).GetAwaiter().GetResult();
}

score 6 · Accepted Answer

已经提到您可以将其模拟为任何其他界面。

var logger = new Mock<ILogger<QueuedHostedService>>();

到目前为止，一切都很好。

不错的是，您可以使用它Moq来验证是否已执行某些调用。例如，在这里我检查日志是否已使用特定的Exception.

logger.Verify(m => m.Log(It.Is<LogLevel>(l => l == LogLevel.Information), 0,
            It.IsAny<object>(), It.IsAny<TaskCanceledException>(), It.IsAny<Func<object, Exception, string>>()));

使用时Verify的重点是针对接口的真实Log方法ILooger而不是扩展方法。

score 6 · Accepted Answer

正如其他答案所建议的那样，通过 mock 很容易ILogger，但是验证是否确实对 logger 进行了调用突然变得更加困难。原因是大多数调用实际上并不属于ILogger接口本身。

所以调用最多的就是调用Log接口唯一方法的扩展方法。原因似乎是，如果您只有一个而不是很多归结为相同方法的重载，则实现接口会更容易。

当然，缺点是验证一个呼叫是否已经发出突然变得更加困难，因为您应该验证的呼叫与您所做的呼叫非常不同。有一些不同的方法可以解决这个问题，我发现用于模拟框架的自定义扩展方法将使它最容易编写。

这是我使用的方法的示例NSubstitute：

public static class LoggerTestingExtensions
{
    public static void LogError(this ILogger logger, string message)
    {
        logger.Log(
            LogLevel.Error,
            0,
            Arg.Is<FormattedLogValues>(v => v.ToString() == message),
            Arg.Any<Exception>(),
            Arg.Any<Func<object, Exception, string>>());
    }

}

这就是它的使用方式：

_logger.Received(1).LogError("Something bad happened");

看起来就像您直接使用该方法一样，这里的技巧是我们的扩展方法获得优先级，因为它在命名空间中比原始方法“更接近”，因此将使用它。

不幸的是，它没有提供我们想要的 100%，即错误消息不会那么好，因为我们不直接检查字符串，而是检查涉及字符串的 lambda，但 95% 总比没有好:) 另外这种方法将使测试代码

PS 对于 Moq，可以使用编写扩展方法的方法Mock<ILogger<T>>来Verify实现类似的结果。

PPS 这在 .Net Core 3 中不再起作用，请查看此线程以获取更多详细信息：https ://github.com/nsubstitute/NSubstitute/issues/597#issuecomment-573742574

score 3 · Accepted Answer

当使用 StructureMap / Lamar 时：

var c = new Container(_ =>
{
    _.For(typeof(ILogger<>)).Use(typeof(NullLogger<>));
});

文件：

score 2 · Accepted Answer

仅仅创建一个虚拟ILogger对象对于单元测试来说不是很有价值。您还应该验证是否进行了日志记录调用。ILogger您可以使用Moq注入模拟，但验证调用可能有点棘手。本文深入探讨了使用 Moq 进行验证。

这是文章中的一个非常简单的示例：

_loggerMock.Verify(l => l.Log(
LogLevel.Information,
It.IsAny<EventId>(),
It.IsAny<It.IsAnyType>(),
It.IsAny<Exception>(),
(Func<It.IsAnyType, Exception, string>)It.IsAny<object>()), Times.Exactly(1));

它验证是否记录了信息消息。但是，如果我们想要验证有关消息的更复杂的信息，例如消息模板和命名属性，则变得更加棘手：

_loggerMock.Verify
(
    l => l.Log
    (
        //Check the severity level
        LogLevel.Error,
        //This may or may not be relevant to your scenario
        It.IsAny<EventId>(),
        //This is the magical Moq code that exposes internal log processing from the extension methods
        It.Is<It.IsAnyType>((state, t) =>
            //This confirms that the correct log message was sent to the logger. {OriginalFormat} should match the value passed to the logger
            //Note: messages should be retrieved from a service that will probably store the strings in a resource file
            CheckValue(state, LogTest.ErrorMessage, "{OriginalFormat}") &&
            //This confirms that an argument with a key of "recordId" was sent with the correct value
            //In Application Insights, this will turn up in Custom Dimensions
            CheckValue(state, recordId, nameof(recordId))
    ),
    //Confirm the exception type
    It.IsAny<NotImplementedException>(),
    //Accept any valid Func here. The Func is specified by the extension methods
    (Func<It.IsAnyType, Exception, string>)It.IsAny<object>()),
    //Make sure the message was logged the correct number of times
    Times.Exactly(1)
);

我确信您可以对其他模拟框架做同样的事情，但ILogger界面确保它很困难。

score 2 · Accepted Answer

我尝试使用 NSubstitute 来模拟 Logger 接口（并且失败，因为Arg.Any<T>()需要一个我无法提供的类型参数），但最终以以下方式创建了一个测试记录器（类似于@jehof 的答案）：

    internal sealed class TestLogger<T> : ILogger<T>, IDisposable
    {
        private readonly List<LoggedMessage> _messages = new List<LoggedMessage>();

        public IReadOnlyList<LoggedMessage> Messages => _messages;

        public void Dispose()
        {
        }

        public IDisposable BeginScope<TState>(TState state)
        {
            return this;
        }

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

        public void Log<TState>(LogLevel logLevel, EventId eventId, TState state, Exception exception, Func<TState, Exception, string> formatter)
        {
            var message = formatter(state, exception);
            _messages.Add(new LoggedMessage(logLevel, eventId, exception, message));
        }

        public sealed class LoggedMessage
        {
            public LogLevel LogLevel { get; }
            public EventId EventId { get; }
            public Exception Exception { get; }
            public string Message { get; }

            public LoggedMessage(LogLevel logLevel, EventId eventId, Exception exception, string message)
            {
                LogLevel = logLevel;
                EventId = eventId;
                Exception = exception;
                Message = message;
            }
        }
    }

您可以轻松访问所有记录的消息并断言随它提供的所有有意义的参数。

score 0 · Accepted Answer

我创建了一个包Moq.ILogger，以便更轻松地测试 ILogger 扩展。

您实际上可以使用以下更接近您的实际代码的内容。

loggerMock.VerifyLog(c => c.LogInformation(
                 "Index page say hello", 
                 It.IsAny<object[]>());

不仅更容易编写新的测试，而且维护也是免费的。

可以在这里找到 repo，并且也有一个 nuget 包（Install-Package ILogger.Moq）。

我也在我的博客上用一个真实的例子来解释它。

简而言之，假设您有以下代码：

public class PaymentsProcessor
{
    private readonly IOrdersRepository _ordersRepository;
    private readonly IPaymentService _paymentService;
    private readonly ILogger<PaymentsProcessor> _logger;

    public PaymentsProcessor(IOrdersRepository ordersRepository, 
        IPaymentService paymentService, 
        ILogger<PaymentsProcessor> logger)
    {
        _ordersRepository = ordersRepository;
        _paymentService = paymentService;
        _logger = logger;
    }

    public async Task ProcessOutstandingOrders()
    {
        var outstandingOrders = await _ordersRepository.GetOutstandingOrders();
        
        foreach (var order in outstandingOrders)
        {
            try
            {
                var paymentTransaction = await _paymentService.CompletePayment(order);
                _logger.LogInformation("Order with {orderReference} was paid {at} by {customerEmail}, having {transactionId}", 
                                       order.OrderReference, 
                                       paymentTransaction.CreateOn, 
                                       order.CustomerEmail, 
                                       paymentTransaction.TransactionId);
            }
            catch (Exception e)
            {
                _logger.LogWarning(e, "An exception occurred while completing the payment for {orderReference}", 
                                   order.OrderReference);
            }
        }
        _logger.LogInformation("A batch of {0} outstanding orders was completed", outstandingOrders.Count);
    }
}

然后你可以写一些测试，比如

[Fact]
public async Task Processing_outstanding_orders_logs_batch_size()
{
    // Arrange
    var ordersRepositoryMock = new Mock<IOrdersRepository>();
    ordersRepositoryMock.Setup(c => c.GetOutstandingOrders())
        .ReturnsAsync(GenerateOutstandingOrders(100));

    var paymentServiceMock = new Mock<IPaymentService>();
    paymentServiceMock
        .Setup(c => c.CompletePayment(It.IsAny<Order>()))
        .ReturnsAsync((Order order) => new PaymentTransaction
        {
            TransactionId = $"TRX-{order.OrderReference}"
        });

    var loggerMock = new Mock<ILogger<PaymentsProcessor>>();

    var sut = new PaymentsProcessor(ordersRepositoryMock.Object, paymentServiceMock.Object, loggerMock.Object);

    // Act
    await sut.ProcessOutstandingOrders();

    // Assert
    loggerMock.VerifyLog(c => c.LogInformation("A batch of {0} outstanding orders was completed", 100));
}

[Fact]
public async Task Processing_outstanding_orders_logs_order_and_transaction_data_for_each_completed_payment()
{
    // Arrange
    var ordersRepositoryMock = new Mock<IOrdersRepository>();
    ordersRepositoryMock.Setup(c => c.GetOutstandingOrders())
        .ReturnsAsync(GenerateOutstandingOrders(100));

    var paymentServiceMock = new Mock<IPaymentService>();
    paymentServiceMock
        .Setup(c => c.CompletePayment(It.IsAny<Order>()))
        .ReturnsAsync((Order order) => new PaymentTransaction
        {
            TransactionId = $"TRX-{order.OrderReference}"
        });

    var loggerMock = new Mock<ILogger<PaymentsProcessor>>();

    var sut = new PaymentsProcessor(ordersRepositoryMock.Object, paymentServiceMock.Object, loggerMock.Object);

    // Act
    await sut.ProcessOutstandingOrders();

    // Assert
    loggerMock.VerifyLog(logger => logger.LogInformation("Order with {orderReference} was paid {at} by {customerEmail}, having {transactionId}",
        It.Is<string>(orderReference => orderReference.StartsWith("Reference")),
        It.IsAny<DateTime>(),
        It.Is<string>(customerEmail => customerEmail.Contains("@")),
        It.Is<string>(transactionId => transactionId.StartsWith("TRX"))),
      Times.Exactly(100));
}

[Fact]
public async Task Processing_outstanding_orders_logs_a_warning_when_payment_fails()
{
    // Arrange
    var ordersRepositoryMock = new Mock<IOrdersRepository>();
    ordersRepositoryMock.Setup(c => c.GetOutstandingOrders())
        .ReturnsAsync(GenerateOutstandingOrders(2));

    var paymentServiceMock = new Mock<IPaymentService>();
    paymentServiceMock
        .SetupSequence(c => c.CompletePayment(It.IsAny<Order>()))
        .ReturnsAsync(new PaymentTransaction
        {
            TransactionId = "TRX-1",
            CreateOn = DateTime.Now.AddMinutes(-new Random().Next(100)),
        })
        .Throws(new Exception("Payment exception"));

    var loggerMock = new Mock<ILogger<PaymentsProcessor>>();

    var sut = new PaymentsProcessor(ordersRepositoryMock.Object, paymentServiceMock.Object, loggerMock.Object);

    // Act
    await sut.ProcessOutstandingOrders();

    // Assert
    loggerMock.VerifyLog(c => c.LogWarning(
                 It.Is<Exception>(paymentException => paymentException.Message.Contains("Payment exception")), 
                 "*exception*Reference 2"));
}

score 0 · Accepted Answer

@Mahmoud Hanafy

我更新了您的答案以适应当前状态。

static class MockLogHelper
{
    public static ISetup<ILogger<T>> MockLog<T>(this Mock<ILogger<T>> logger, LogLevel level)
    {
        return logger.Setup(x => x.Log(level, It.IsAny<EventId>(), It.IsAny<It.IsAnyType>(), It.IsAny<Exception>(), (Func<It.IsAnyType, Exception, string>)It.IsAny<object>()));
        //return logger.Setup(x => x.Log(level, It.IsAny<EventId>(), It.IsAny<object>(), It.IsAny<Exception>(), It.IsAny<Func<object, Exception, string>>()));
    }

    private static Expression<Action<ILogger<T>>> Verify<T>(LogLevel level)
    {
        return x => x.Log(level, 0, It.IsAny<It.IsAnyType>(), It.IsAny<Exception>(), (Func<It.IsAnyType, Exception, string>)It.IsAny<object>());
        //return x => x.Log(level, 0, It.IsAny<object>(), It.IsAny<Exception>(), It.IsAny<Func<object, Exception, string>>());
    }

    public static void Verify<T>(this Mock<ILogger<T>> mock, LogLevel level, Times times)
    {
        mock.Verify(Verify<T>(level), times);
    }
}

score -1 · Accepted Answer

使用Telerik Just Mock创建记录器的模拟实例：

using Telerik.JustMock;
...
context = new XDbContext(Mock.Create<ILogger<XDbContext>>());

score -1 · Accepted Answer

使用 NullLogger - 什么都不做的简约记录器。

public interface ILoggingClass
{
   public void LogCritical(Exception exception);
}

public class LoggingClass : ILoggingClass
{
    private readonly ILogger<LoggingClass> logger;

    public LoggingClass(ILogger<LoggingClass> logger) =>
            this.logger = logger;

    public void LogCritical(Exception exception) =>
        this.logger.LogCritical(exception, exception.Message);
}

并在测试方法使用中，

ILogger<LoggingClass> logger = new NullLogger<LoggingClass>();
LoggingClass loggingClass = new LoggingClass(logger);

并将 loggingClass 传递给服务进行测试。

c# - 如何在 ASP.NET Core 中使用 ILogger 进行单元测试

16 回答 16

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