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Using NLog in your Unit Test Framework

Published Sep 15, 2015

So I was writing some automation tests and I wanted to have some in-depth logging to know what is going on when the tests fail for better diagnostics (same as you would in any normal application).

So it occurred to me, why re-invent the wheel creating a logging framework when there are some really good ones out there? I chose NLog, I had a small amount of experience with NLog before but not that much (I primarily used Elmah)

I did a bit of research and found that people wanted logging in their Unit Tests but there were not that many solutions so I just went with it and implemented NLog into my Unit Test Project. Here is what I did:

Installed NLog into my Unit Test Project via Nuget Install-Package NLog Great!

So since a unit test project doesn’t really need any configuration files I needed to create an App.config for NLog to read it’s configuration. I added the following configuration elements between <configuration>:

    <section name="nlog" type="NLog.Config.ConfigSectionHandler, NLog" />

<nlog xmlns="http://www.nlog-project.org/schemas/NLog.xsd"
        <target name="file"
                layout="${date} ${logger} ${level}: ${message}"
                fileName="C:\Logs\${shortdate}.log" />
        <logger name="*" minlevel="Trace" writeTo="file"/>

So since we need this app.config with the actual unit tests we need to make sure in out TestSettings we add this as a deployment item. (If you do not have a TestSettings file under your solution you will need to create it: Right click your solution in Solution Explorer, Add > New Item, Under Test Settings menu there is the TestSettings file.) So open up the TestSettings file and navigate to the Deployment menu and ensure that the ‘Enable Deployment’ checkbox is checked. Then Press ‘Add File’ and navigate to your app.config and then press Apply!

Now when we run the unit tests the app.config will be deployed with the relevant .dll. Now you can just use NLog like you would usually!

var logger = LogManager.GetCurrentClassLogger();
logger.Debug("This is a debug message!");

You could just finish there and be done with it, but usually any logging implementations I write I like to implement an interface so I can easily swap out the Logging framework for another and also Mock out the Logger (not this type).


public interface ILogger
    void Trace(string message);
    void Info(string message);
    void Warn(string message);
    void Debug(string message);
    void Error(string message);
    void Error(string message, Exception x);
    void Error(Exception x);
    void Fatal(string message);
    void Fatal(Exception x);


public class NLogLogger : ILogger
        private readonly Logger _logger;
        public NLogLogger(Type classType)
            _logger = LogManager.GetLogger(classType.Name);
        public void Trace(string message)
        public void Info(string message)
        public void Warn(string message)
        public void Debug(string message)
        public void Error(string message)
        public void Error(Exception x)
        public void Error(string message, Exception x)
            _logger.Error(x, message);
        public void Fatal(string message)
        public void Fatal(Exception x)

So since we are using a wrapper with the NLog implementation we are going to need to do something slightly different as you can see in the NLogLogger constructor. We cannot call LogManager.GetCurrentClassLogger() since it will always be NLogLogger so we need to pass it the class type.

 public class LoggerTestClass
     public LoggerTestClass()
         Logger = new NLogLogger(typeof(LoggerTestClass));
     private ILogger Logger { get; set; }
     public void LogUnitTest()
         Logger.Fatal("Fatal Exception!");

Then you are all set! You will get some nice formatted logs from your Unit tests.