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How to redirect the standard console output, to assert logmessages written by log4net.

How to redirect the standard console output, to assert logmessages written by log4net.

By using a log4net ConsoleAppender, you can write all log messages in your application to the console. These message will show up in the Microsoft Visual Studio output window. I needed a way to redirect the messages written to the console, so I could verify if the correct messages were send to the console. For this task I redirected the standard console output in my unit test:



using System;
using System.IO;
using System.Text;
using log4net;
using log4net.Config;
using Microsoft.VisualStudio.TestTools.UnitTesting;

namespace TestProject1
    public class UnitTest1
        public void TestMethod1()
            // Save original console output writer.
            TextWriter originalConsole = Console.Out;

            // Configure log4net based on the App.config

            var builder = new StringBuilder();
            using (var writer = new StringWriter(builder))
                // Redirect all Console messages to the StringWriter.

                // Log a debug message.
                ILog logger = LogManager.GetLogger("Unittest logger");
                logger.Debug("This is a debug message");

            // Get all messages written to the console.
            string consoleOutput = string.Empty;
            using (var reader = new StringReader(builder.ToString()))
                consoleOutput = reader.ReadToEnd();

            // Assert.
            string expected = "This is a debug message" + Environment.NewLine;
            Assert.AreEqual(expected, consoleOutput);

            // Redirect back to original console output.



<?xml version="1.0"?>
    <section name="log4net" type="log4net.Config.Log4NetConfigurationSectionHandler,log4net"/>
    <appender name="ConsoleAppender" type="log4net.Appender.ConsoleAppender">
      <layout type="log4net.Layout.PatternLayout">
        <conversionPattern value="%message%newline" />
      <level value="DEBUG"/>
      <appender-ref ref="ConsoleAppender" />
    <supportedRuntime version="v4.0" sku=".NETFramework,Version=v4.0"/>

Microsoft Visual Studio




I used NuGet to add a reference to the latest log4net build.

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