public class MyTests
{
    private readonly ITestOutputHelper _output;
    
    public MyTests(ITestOutputHelper testOutputHelper)
    {
        _output = testOutputHelper;
    }
}

private void LogSection(string title)
{
    _output.WriteLine($"\n=== {title} ===");
}

private void LogKeyValue(string key, object value)
{
    _output.WriteLine($"{key}: {value}");
}

private void LogTimestamp(DateTime time)
{
    _output.WriteLine($"執行時間: {time:yyyy-MM-dd HH:mm:ss.fff}");
}

// ❌ 錯誤：直接 Mock 擴充方法會失敗
logger.Received().LogError(Arg.Any<string>());

// ✅ 正確：攔截底層方法
logger.Received().Log(
    LogLevel.Error,
    Arg.Any<EventId>(),
    Arg.Is<object>(o => o.ToString().Contains("預期訊息")),
    Arg.Any<Exception>(),
    Arg.Any<Func<object, Exception, string>>()
);

public abstract class AbstractLogger<T> : ILogger<T>
{
    public IDisposable BeginScope<TState>(TState state) 
        => null;
    
    public bool IsEnabled(LogLevel logLevel) 
        => true;
    
    public void Log<TState>(
        LogLevel logLevel,
        EventId eventId,
        TState state,
        Exception exception,
        Func<TState, Exception, string> formatter)
    {
        Log(logLevel, exception, state?.ToString() ?? string.Empty);
    }
    
    public abstract void Log(LogLevel logLevel, Exception ex, string information);
}

var logger = Substitute.For<AbstractLogger<MyService>>();
// 現在可以簡單驗證
logger.Received().Log(LogLevel.Error, Arg.Any<Exception>(), Arg.Is<string>(s => s.Contains("錯誤訊息")));

public class XUnitLogger<T> : ILogger<T>
{
    private readonly ITestOutputHelper _testOutputHelper;
    
    public XUnitLogger(ITestOutputHelper testOutputHelper)
    {
        _testOutputHelper = testOutputHelper;
    }
    
    public void Log<TState>(LogLevel logLevel, EventId eventId, TState state, 
        Exception exception, Func<TState, Exception, string> formatter)
    {
        var message = formatter(state, exception);
        _testOutputHelper.WriteLine($"[{DateTime.Now:HH:mm:ss.fff}] [{logLevel}] [{typeof(T).Name}] {message}");
        if (exception != null)
        {
            _testOutputHelper.WriteLine($"Exception: {exception}");
        }
    }
    
    // 其他必要的介面實作...
}

public class CompositeLogger<T> : ILogger<T>
{
    private readonly ILogger<T>[] _loggers;
    
    public CompositeLogger(params ILogger<T>[] loggers)
    {
        _loggers = loggers;
    }
    
    public void Log<TState>(LogLevel logLevel, EventId eventId, TState state,
        Exception exception, Func<TState, Exception, string> formatter)
    {
        foreach (var logger in _loggers)
        {
            logger.Log(logLevel, eventId, state, exception, formatter);
        }
    }
    
    // 其他介面實作會委派給所有內部 logger...
}

// 同時進行行為驗證與測試輸出
var mockLogger = Substitute.For<AbstractLogger<MyService>>();
var xunitLogger = new XUnitLogger<MyService>(_output);
var compositeLogger = new CompositeLogger<MyService>(mockLogger, xunitLogger);

var service = new MyService(compositeLogger);

[Fact]
public async Task ProcessLargeDataSet_效能測試()
{
    // Arrange
    var stopwatch = Stopwatch.StartNew();
    var checkpoints = new List<(string Stage, TimeSpan Elapsed)>();
    
    _output.WriteLine("開始處理大型資料集...");
    
    // Act & Monitor
    await processor.LoadData(dataSet);
    checkpoints.Add(("資料載入", stopwatch.Elapsed));
    _output.WriteLine($"資料載入完成: {stopwatch.Elapsed.TotalMilliseconds:F2} ms");
    
    await processor.ProcessData();
    checkpoints.Add(("資料處理", stopwatch.Elapsed));
    _output.WriteLine($"資料處理完成: {stopwatch.Elapsed.TotalMilliseconds:F2} ms");
    
    stopwatch.Stop();
    
    // Assert & Report
    _output.WriteLine("\n=== 效能報告 ===");
    foreach (var (stage, elapsed) in checkpoints)
    {
        _output.WriteLine($"{stage}: {elapsed.TotalMilliseconds:F2} ms");
    }
}

public abstract class DiagnosticTestBase
{
    protected readonly ITestOutputHelper Output;
    
    protected DiagnosticTestBase(ITestOutputHelper output)
    {
        Output = output;
    }
    
    protected void LogTestStart(string testName)
    {
        Output.WriteLine($"\n=== {testName} ===");
        Output.WriteLine($"執行時間: {DateTime.Now:yyyy-MM-dd HH:mm:ss.fff}");
    }
    
    protected void LogTestData(object data)
    {
        Output.WriteLine($"測試資料: {JsonSerializer.Serialize(data, new JsonSerializerOptions { WriteIndented = true })}");
    }
    
    protected void LogAssertionFailure(string field, object expected, object actual)
    {
        Output.WriteLine("\n=== 斷言失敗 ===");
        Output.WriteLine($"欄位: {field}");
        Output.WriteLine($"預期值: {expected}");
        Output.WriteLine($"實際值: {actual}");
    }
}