c# - 如何解决 XUnit 测试失败并在 "Run All"下的 NLog 目标中断言消息的情况

Question

这是我的环境:

• Visual Studio 2017
• 项目的.NET运行时版本为4.6.2
• XUnit 版本 2.3.1
• NLog 版本 4.4.12
• 流利断言 4.19.4

问题是:

当我单独运行测试时，它们通过了，但是当我通过测试资源管理器中的“全部运行”按钮运行时，我遇到了失败，并且当重复运行后续失败的任务时，它们最终都通过了。还想指出我没有并行运行测试。测试的性质使得被测代码发出最终在自定义 NLog 目标中结束的日志信息。这是一个示例程序，可以运行它来重现问题。

using FluentAssertions;
using NLog;
using NLog.Common;
using NLog.Config;
using NLog.Targets;
using System;
using System.Collections.Concurrent;
using System.IO;
using Xunit;

namespace LoggingTests
{
    [Target("test-target")]
    public class TestTarget : TargetWithLayout
    {
        public ConcurrentBag<string> Messages = new ConcurrentBag<string>();

        public TestTarget(string name)
        {
            Name = name;
        }

        protected override void Write(LogEventInfo logEvent)
        {
            Messages.Add(Layout.Render(logEvent));
        }
    }

    class Loggable
    {
        private Logger _logger;

        public Loggable()
        {
            _logger = LogManager.GetCurrentClassLogger();
        }

        private void Log(LogLevel level,
                         Exception exception,
                         string message,
                         params object[] parameters)
        {
            LogEventInfo log_event = new LogEventInfo();
            log_event.Level = level;
            log_event.Exception = exception;
            log_event.Message = message;
            log_event.Parameters = parameters;
            log_event.LoggerName = _logger.Name;
            _logger.Log(log_event);
        }

        public void Debug(string message)
        {
            Log(LogLevel.Debug,
                null,
                message,
                null);
        }

        public void Error(string message)
        {
            Log(LogLevel.Error,
                null,
                message,
                null);
        }

        public void Info(string message)
        {
            Log(LogLevel.Info,
                null,
                message,
                null);
        }

        public void Fatal(string message)
        {
            Log(LogLevel.Fatal,
                null,
                message,
                null);
        }
    }

    public class Printer
    {
        public delegate void Print(string message);
        private Print _print_function;

        public Printer(Print print_function)
        {
            _print_function = print_function;
        }

        public void Run(string message_template,
                        int number_of_times)
        {
            for (int i = 0; i < number_of_times; i++)
            {
                _print_function($"{message_template} - {i}");
            }
        }
    }

    public abstract class BaseTest
    {
        protected string _target_name;

        public BaseTest(LogLevel log_level)
        {
            if (LogManager.Configuration == null)
            {
                LogManager.Configuration = new LoggingConfiguration();
                InternalLogger.LogLevel = LogLevel.Debug;
                InternalLogger.LogFile = Path.Combine(Environment.CurrentDirectory,
                                                      "nlog_debug.txt");
            }

            // Register target:
            _target_name = GetType().Name;
            Target.Register<TestTarget>(_target_name);

            // Create Target:
            TestTarget t = new TestTarget(_target_name);
            t.Layout = "${message}";

            // Add Target to configuration:
            LogManager.Configuration.AddTarget(_target_name,
                                               t);

            // Add a logging rule pertaining to the above target:
            LogManager.Configuration.AddRule(log_level,
                                             log_level,
                                             t);

            // Because configuration has been modified programatically, we have to reconfigure all loggers:
            LogManager.ReconfigExistingLoggers();
        }
        protected void AssertTargetContains(string message)
        {
            TestTarget target = (TestTarget)LogManager.Configuration.FindTargetByName(_target_name);
            target.Messages.Should().Contain(message);
        }
    }

    public class TestA : BaseTest
    {
        public TestA() : base(LogLevel.Info)
        {
        }

        [Fact]
        public void SomeTest()
        {
            int number_of_times = 100;
            (new Printer((new Loggable()).Info)).Run(GetType().Name, 
                                                     number_of_times);
            for (int i = 0; i < number_of_times; i++)
            {
                AssertTargetContains($"{GetType().Name} - {i}");
            }
        }
    }

    public class TestB : BaseTest
    {
        public TestB() : base(LogLevel.Debug)
        {
        }

        [Fact]
        public void SomeTest()
        {
            int number_of_times = 100;
            (new Printer((new Loggable()).Debug)).Run(GetType().Name,
                                                     number_of_times);
            for (int i = 0; i < number_of_times; i++)
            {
                AssertTargetContains($"{GetType().Name} - {i}");
            }
        }
    }

    public class TestC : BaseTest
    {
        public TestC() : base(LogLevel.Error)
        {
        }

        [Fact]
        public void SomeTest()
        {
            int number_of_times = 100;
            (new Printer((new Loggable()).Error)).Run(GetType().Name,
                                                     number_of_times);
            for (int i = 0; i < number_of_times; i++)
            {
                AssertTargetContains($"{GetType().Name} - {i}");
            }
        }
    }

    public class TestD : BaseTest
    {
        public TestD() : base(LogLevel.Fatal)
        {
        }

        [Fact]
        public void SomeTest()
        {
            int number_of_times = 100;
            (new Printer((new Loggable()).Fatal)).Run(GetType().Name,
                                                     number_of_times);
            for (int i = 0; i < number_of_times; i++)
            {
                AssertTargetContains($"{GetType().Name} - {i}");
            }
        }
    }
}

上面的测试代码运行的比较好。在按照消息进行一些较早的故障排除后，我似乎没有在调用 LogManager.ReconfigExistingLoggers();因为配置是以编程方式创建的(在测试类的构造函数中)。这是 LogManager 源代码中的注释:

/// Loops through all loggers previously returned by GetLogger.
/// and recalculates their target and filter list. Useful after modifying the configuration programmatically
/// to ensure that all loggers have been properly configured.

之后所有测试都按预期运行，偶尔会出现如下所示的故障:

我现在想知道在我的测试设置中是否还有什么我应该保护的，或者这是一个错误 NLog。任何关于如何修复我的测试设置或对设置进行故障排除的建议都将非常受欢迎。提前致谢。

---

更新

• 已更改 List<LogData>至 ConcurrentBag<LogData> .然而，这并没有改变问题。问题仍然是消息没有及时到达集合中。
• 重新表述问题并将之前的代码示例替换为实际示例(可以运行以重现问题)+ 问题的屏幕截图。
• 改进的测试运行得更好但偶尔会由于来自 NLog 本身的异常而失败(添加的屏幕截图)。

Answer 1

上述问题恰好与 VisualStudio 中的 XUnit Runner 有关。尽管我禁用了“不要并行运行测试”，但测试以某种方式并行运行。 @rolf-kristensen 在另一个 NLog 问题(引用:https://github.com/NLog/NLog/issues/2525)中指出他添加了以下内容:

[assembly: Xunit.CollectionBehavior(DisableTestParallelization = true)]

在 AssemblyInfo.cs 文件中。 XUnit 的页面上也提到了此配置(引用:https://xunit.github.io/docs/running-tests-in-parallel.html - 更改默认行为)