你如何模拟 ILogger LogInformation

Question

我有一个接收 ILogger 的类，我想模拟 LogInformation 调用，但这是一个扩展方法。我如何为此进行适当的设置调用？

Answer 1

如果您使用的是 Moq >= 4.13，这里是一种模拟方法ILogger：

logger.Verify(x => x.Log(
    It.IsAny<LogLevel>(),
    It.IsAny<EventId>(),
    It.IsAny<It.IsAnyType>(),
    It.IsAny<Exception>(),
    (Func<It.IsAnyType, Exception, string>)It.IsAny<object>()));

你可以改变的It.IsAny<LogLevel>()，It.IsAny<EventId>()和It.IsAny<Exception>()存根更具体，但使用It.IsAnyType是必要的，因为FormattedLogValues现在internal。

参考：ILogger.Log 中的 TState 以前是对象，现在是 FormattedLogValues

Answer 2

带有回调的示例，使用 Moq 4.14.5 进行测试。有关此Github 问题的更多信息

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

logger.Setup(x => x.Log(
    It.IsAny<LogLevel>(),
    It.IsAny<EventId>(),
    It.IsAny<It.IsAnyType>(),
    It.IsAny<Exception>(),
    (Func<It.IsAnyType, Exception, string>)It.IsAny<object>()))
    .Callback(new InvocationAction(invocation =>
    {
        var logLevel = (LogLevel)invocation.Arguments[0]; // The first two will always be whatever is specified in the setup above
        var eventId = (EventId)invocation.Arguments[1];  // so I'm not sure you would ever want to actually use them
        var state = invocation.Arguments[2];
        var exception = (Exception?)invocation.Arguments[3];
        var formatter = invocation.Arguments[4];

        var invokeMethod = formatter.GetType().GetMethod("Invoke");
        var logMessage = (string)invokeMethod?.Invoke(formatter, new[] { state, exception });
    }));

一个完整的 UnitTesting 通用辅助类

public static class LoggerHelper
{
    public static Mock<ILogger<T>> GetLogger<T>()
    {
        var logger = new Mock<ILogger<T>>();

        logger.Setup(x => x.Log(
            It.IsAny<LogLevel>(),
            It.IsAny<EventId>(),
            It.IsAny<It.IsAnyType>(),
            It.IsAny<Exception>(),
            (Func<It.IsAnyType, Exception, string>)It.IsAny<object>()))
            .Callback(new InvocationAction(invocation =>
            {
                var logLevel = (LogLevel)invocation.Arguments[0]; // The first two will always be whatever is specified in the setup above
                var eventId = (EventId)invocation.Arguments[1];  // so I'm not sure you would ever want to actually use them
                var state = invocation.Arguments[2];
                var exception = (Exception?)invocation.Arguments[3];
                var formatter = invocation.Arguments[4];

                var invokeMethod = formatter.GetType().GetMethod("Invoke");
                var logMessage = (string)invokeMethod?.Invoke(formatter, new[] { state, exception });

                Trace.WriteLine(logMessage);
            }));

        return logger;
    }
}

Answer 3

在这种情况下，“假”课程可能比起订量更容易。创建起来需要多一点工作，但是您可以永远重复使用它，并且它比 Moq 回调更容易阅读和使用。（我喜欢 Moq，但当有更简单的方法时就不喜欢。）

对于大多数用例，这将按原样工作，或者您可以对其进行调整。

using System;
using System.Collections.Generic;
using System.Linq;
using Microsoft.Extensions.Logging;

public class FakeLogger<T> : ILogger, ILogger<T>
{
    public List<LogEntry> LogEntries { get; } = new List<LogEntry>();

    public IEnumerable<LogEntry> InformationEntries =>
        LogEntries.Where(e => e.LogLevel == LogLevel.Information);

    public IEnumerable<LogEntry> WarningEntries =>
        LogEntries.Where(e => e.LogLevel == LogLevel.Warning);

    public IEnumerable<LogEntry> ErrorEntries =>
        LogEntries.Where(e => e.LogLevel == LogLevel.Error);

    public void Log<TState>(LogLevel logLevel, EventId eventId, TState state, Exception exception, Func<TState, Exception, string> formatter)
    {
        LogEntries.Add(new LogEntry(logLevel, eventId, state, exception));
    }

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

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

    public class LoggingScope : IDisposable
    {
        public void Dispose()
        {
        }
    }
}

public class LogEntry
{
    public LogEntry(LogLevel logLevel, EventId eventId, object state, Exception exception)
    {
        LogLevel = logLevel;
        EventId = eventId;
        State = state;
        Exception = exception;
    }

    public LogLevel LogLevel { get; }
    public EventId EventId { get; }
    public object State { get; }
    public Exception Exception { get; }
    public string Message => State?.ToString() ?? string.Empty;
    public Dictionary<string, object> Params => (State as IReadOnlyList<KeyValuePair<string, object?>>)!.ToDictionary(key => key.Key, value => value.Value)!;
    public string FormatString => (string)Params["{OriginalFormat}"];
}

创建一个实例并将其作为记录器注入到您的测试类中。然后您可以查看LogEntries集合中的对象以了解记录的内容。

的类型State通常为FormattedLogValues，但您可以调用State.ToString()并仅获取字符串值。

Answer 4

如果你有一个logger( new Mock<ILogger<ReplaceWithYourObject>>()) 模拟注入到 ctor 中。那么这应该有助于验证日志消息和日志级别。

logger.Verify(x => x.Log(
       LogLevel.Information, //Change LogLevel as required
       It.IsAny<EventId>(),
       It.Is<It.IsAnyType>((object v, Type _) => 
       v.ToString().Contains("MessageToVerify")), // Change MessageToVerify as required
       It.IsAny<Exception>(),
       (Func<It.IsAnyType, Exception, string>)It.IsAny<object>()));

Answer 5

ILogger 通常通过扩展方法、LogWarning、LogError 等使用。

就我而言，我对 LogWarning 方法感兴趣，在查看代码后，该方法从 ILogger 调用 Log 方法。为了用 Moq 模拟它，这就是我最终做的：

     var list = new List<string>();
                var logger = new Mock<ILogger>();
                logger
                    .Setup(l => l.Log<FormattedLogValues>(LogLevel.Warning, It.IsAny<EventId>(), It.IsAny<FormattedLogValues>(), It.IsAny<Exception>(), It.IsAny<Func<FormattedLogValues, Exception, string>>()))
                    .Callback(
                    delegate (LogLevel logLevel, EventId eventId, FormattedLogValues state, Exception exception, Func<FormattedLogValues, Exception, string> formatter)
                    {
                        list.Add(state.ToString());
                    });

在较新版本的 .NET Core 3.0 中，这不起作用。因为 FormattedLogValues 是内部类型。您需要将最小起订量版本更新为至少：

`<PackageReference Include="Moq" Version="4.16.0" />`

更新后Moq解决方法是这样的：

            var log = new List<string>();
            var mockLogger = new Mock<ILogger>();
            mockLogger.Setup(
                l => l.Log(
                    It.IsAny<LogLevel>(),
                    It.IsAny<EventId>(),
                    It.IsAny<It.IsAnyType>(),
                    It.IsAny<Exception>(),
                    (Func<It.IsAnyType, Exception, string>)It.IsAny<object>()))
                .Callback((IInvocation invocation) =>
                {
                    var logLevel = (LogLevel)invocation.Arguments[0];
                    var eventId = (EventId)invocation.Arguments[1];
                    var state = (IReadOnlyCollection<KeyValuePair<string, object>>)invocation.Arguments[2];
                    var exception = invocation.Arguments[3] as Exception;
                    var formatter = invocation.Arguments[4] as Delegate;
                    var formatterStr = formatter.DynamicInvoke(state, exception);
                    log.Add(
                      $"{logLevel} - {eventId.Id} - Testing - {formatterStr}");
                });

注意特殊的 cast:(Func<It.IsAnyType, Exception, string>)It.IsAny<object>())以及处理参数的 IInvocation 。

Answer 6

这就是我对Moq (v4.10.1) 框架的解决方法。

public static class TestHelper
{ 

    public static Mock<ILogger<T>> GetMockedLoggerWithAutoSetup<T>()
    {
        var logger = new Mock<ILogger<T>>();

        logger.Setup<object>(x => x.Log(
       It.IsAny<LogLevel>(),
       It.IsAny<EventId>(),
       It.IsAny<object>(),
       It.IsAny<Exception>(),
       It.IsAny<Func<object, Exception, string>>()));

        return logger;
    }

    public static void VerifyLogMessage<T>(Mock<ILogger<T>> mockedLogger, LogLevel logLevel, Func<string, bool> predicate, Func<Times> times)
    {
        mockedLogger.Verify(x => x.Log(logLevel, 0, It.Is<object>(p => predicate(p.ToString())), null, It.IsAny<Func<object, Exception, string>>()), times);
    }
}

——

public class Dummy
{

}

[Fact]
public void Should_Mock_Logger()
{
    var logger = TestHelper.GetMockedLoggerWithAutoSetup<Dummy>();
    logger.Object.LogInformation("test");
    TestHelper.VerifyLogMessage<Dummy>(logger, LogLevel.Information, msg => msg == "test", Times.Once);
}

——

事情是，

如果我选择了其他<TCustom>比<object>对logger.Setup()，它会失败上Verify步说，0话费被用于制作x.Log<TCustom>和展示给打了一个电话x.Log<object>。所以我将我的通用记录器设置为模拟Log<object>(..)方法。