ILogger.cs

using System;
using System.Collections.Generic;
using System.Linq;
using System.Text;

namespace Github.Gist.Logging {
    public interface ILogger {

        void Warn(string s);
        void Warn(string s, Exception ex);
        void WarnFormat(string s, params object [] args);

        void Info(string s);
        void Info(string s, Exception ex);
        void InfoFormat(string s, params object[] args);

        void Debug(string s);
        void Debug(string s, Exception ex);
        void DebugFormat(string s, params object[] args);

    }
}

Log4NetLogger.cs

using System;
using log4net;
using System.Reflection;

namespace Github.Gist.Logging {
    /// <summary>
    /// log4net wrapper to allow easier unit testing (by testing against the ILogger interface)
    /// </summary>
    public class Log4NetLogger : ILogger {

        private static readonly ILog Log = LogManager.GetLogger(MethodBase.GetCurrentMethod().DeclaringType);

        #region ILogger Members

        public void Warn(string s) {
            Log.Warn(s);
        }

        public void Warn(string s, Exception ex) {
            Log.Warn(s, ex);
        }

        public void WarnFormat(string s, params object [] args) {
            Log.WarnFormat(s, args);
        }

        public void Info(string s) {
            Log.Info(s);
        }

        public void Info(string s, Exception ex) {
            Log.Info(s, ex);
        }

        public void InfoFormat(string s, params object[] args) {
            Log.InfoFormat(s, args);
        }

        public void Debug(string s) {
            Log.Debug(s);
        }

        public void Debug(string s, Exception ex) {
            Log.Debug(s, ex);
        }

        public void DebugFormat(string s, params object[] args) {
            Log.DebugFormat(s, args);
        }

        #endregion
    }
}