C#Static Readonly log4net logger,在Unit Test中改变记录器的方法有哪些？

Question

我的班级有这一行:

private static readonly ILog log = LogManager.GetLogger(typeof(Prim));

当我进行单元测试时,我无法将moq记录器注入此接口,因此我可以计算日志调用.

有没有办法做到这一点？Log4net建议记录器使用静态只读模式.处理它的最佳方法是什么？

Answer 1

虽然log4net推荐使用此模式,但没有什么可以阻止您在类外部实例化记录器并注入它.大多数IoC可以配置为注入一个相同的实例.这样,对于您的单元测试,您可以注入模拟.

我建议使用LogManager.GetLogger的包装器,它每个类型总是返回一个和相同的记录器实例:

namespace StackOverflowExample.Moq
{
    public interface ILogCreator
    {
        ILog GetTypeLogger<T>() where T : class;
    }

    public class LogCreator : ILogCreator
    {
        private static readonly IDictionary<Type, ILog> loggers = new Dictionary<Type, ILog>();
        private static readonly object lockObject;

        public ILog GetTypeLogger<T>() where T : class
        {
            var loggerType = typeof (T);
            if (loggers.ContainsKey(loggerType))
            {
                return loggers[typeof (T)];
            }

            lock (lockObject)
            {
                if (loggers.ContainsKey(loggerType))
                {
                    return loggers[typeof(T)];
                }
                var logger = LogManager.GetLogger(loggerType);
                loggers[loggerType] = logger;
                return logger;
            }
        }
    }

    public class ClassWithLogger
    {
        private readonly ILog logger;
        public ClassWithLogger(ILogCreator logCreator)
        {
            logger = logCreator.GetTypeLogger<ClassWithLogger>();
        }

        public void DoSomething()
        {
            logger.Debug("called");
        }
    }

    [TestFixture]
    public class Log4Net
    {
        [Test]
        public void DoSomething_should_write_in_debug_logger()
        {
            //arrange
            var logger = new Mock<ILog>();
            var loggerCreator = Mock.Of<ILogCreator>(
                c =>
                c.GetTypeLogger<ClassWithLogger>() == logger.Object);

            var sut = new ClassWithLogger(loggerCreator);

            //act
            sut.DoSomething();

            //assert
            logger.Verify(l=>l.Debug("called"), Times.Once());
        }
    }
}