Can a unit test project load the target application's app.config file?

Question

I am unit testing a .NET application (.exe) that uses an app.config file to load configuration properties. The unit test application itself does not have an app.config file.

When I try to unit test a method that utilizes any of the configuration properties, they return null. I'm assuming this is because the unit test application is not going to load in the target application's app.config.

Is there a way to override this or do I have to write a script to copy the contents of the target app.config to a local app.config?

This post kind-of asks this question but the author is really looking at it from a different angle than I am.

EDIT: I should mention that I'm using VS08 Team System for my unit tests.

Jeromy_Irvine_8223 · Answer

The simplest way to do this is to add the .config file in the deployment section on your unit test.

To do so, open the .testrunconfig file from your Solution Items. In the Deployment section, add the output .config files from your project's build directory (presumably bin\Debug).

Anything listed in the deployment section will be copied into the test project's working folder before the tests are run, so your config-dependent code will run fine.

Edit: I forgot to add, this will not work in all situations, so you may need to include a startup script that renames the output .config to match the unit test's name.

user_30809 · Answer

Whether you're using Team System Test or NUnit, the best practice is to create a separate Class Library for your tests. Simply adding an App.config to your Test project will automatically get copied to your bin folder when you compile.

If your code is reliant on specific configuration tests, the very first test I would write validates that the configuration file is available (so that I know I'm not insane) :

And the test:

[TestFixture]
public class GeneralFixture
{
     [Test]
     public void VerifyAppDomainHasConfigurationSettings()
     {
          string value = ConfigurationManager.AppSettings["TestValue"];
          Assert.IsFalse(String.IsNullOrEmpty(value), "No App.Config found.");
     }
}

Ideally, you should be writing code such that your configuration objects are passed into your classes. This not only separates you from the configuration file issue, but it also allows you to write tests for different configuration scenarios.

public class MyObject
{
     public void Configure(MyConfigurationObject config)
     {
          _enabled = config.Enabled;
     }

     public string Foo()
     {
         if (_enabled)
         {
             return "foo!";
         }
         return String.Empty;
     }

     private bool _enabled;
}

[TestFixture]
public class MyObjectTestFixture
{
     [Test]
     public void CanInitializeWithProperConfig()
     {
         MyConfigurationObject config = new MyConfigurationObject();
         config.Enabled = true;

         MyObject myObj = new MyObject();
         myObj.Configure(config);

         Assert.AreEqual("foo!", myObj.Foo());
     }
}

Cory_Foy_4083 · Answer

If you are using NUnit, take a look at this post. Basically you'll need to have your app.config in the same directory as your .nunit file.

Daok_13913 · Answer

I use NUnit and in my project directory I have a copy of my App.Config that I change some configuration (example I redirect to a test database...). You need to have it in the same directory of the tested project and you will be fine.

user_1037314 · Answer

Your unit tests are considered as an environment that runs your code to test it. Just like any normal environment, you have i.e. staging/production. You may need to add a .config file for your test project as well. A workaround is to create a class library and convert it to Test Project by adding necessary NuGet packages such as NUnit and NUnit Adapter. it works perfectly fine with both Visual Studio Test Runner and Resharper and you have your app.config file in your test project.

And finally debugged my test and value from App.config:

Can a unit test project load the target application's app.config file?

11 Answers