log4netrecorder.cs

[TestFixture]
    public class RecordTest
    {
        [Test]
        public void DoTest()
        {
            var testing = Log4NetTestHelper.RecordLog(() =>
            {
                var log = LogManager.GetLogger(typeof (RecordTest));
                log.Error("Testing!");
            });

            Assert.AreEqual("Testing!", testing[0]);
        }
    }

    public static class Log4NetTestHelper
    {
        public static string[] RecordLog(Action action)
        {
            if (!LogManager.GetRepository().Configured)
                BasicConfigurator.Configure();
            var logMessages = new List<string>();
            var root = ((log4net.Repository.Hierarchy.Hierarchy)LogManager.GetRepository()).Root;
            var attachable = root as IAppenderAttachable;

            var appender = new MemoryAppender();
            if (attachable != null)
                attachable.AddAppender(appender);

            action();

            var loggingEvents = appender.GetEvents();
            foreach (var loggingEvent in loggingEvents)
            {
                var stringWriter = new StringWriter();
                loggingEvent.WriteRenderedMessage(stringWriter);
                logMessages.Add(stringWriter.ToString());
            }
            if (attachable != null)
                attachable.RemoveAppender(appender);

            return logMessages.ToArray();
        }
    }