Question

My web application depends on a web.config entry being a certain value (like FEATURE_ACTIVATED=true) so how do I test the function that reads this web.config entry?

I’d like to avoid copying the web.config entries to an app.config in the unit testing project, as it takes extra effort to synchronize the files.

Answer 1

Pull out the code that reads configuration data, then use dependency injection paired with a mock object, or a mocking framework in your tests.

public interface IConfiguration
{
  bool IsAwesomeFeatureActivated { get; }
}

public class Configuration: IConfiguration
{
  public bool IsAwesomeFeatureActivated
  { 
    get { /* get config value */ }
  }
}

public class AwesomeFeature
{
  private IConfiguration _configuration;

  public AwesomeFeature(IConfiguration configuration)
  {
    _configuration = configuration;
  }

  public void ExecuteFeature()
  {
    if(! _configuration.IsAwesomeFeatureActivated) return;
    // do awesome feature functionality
  }
}

public class MockConfiguration: IConfiguration
{
  private bool _isAwesomeFeatureActivated;
  public void SetIsAwesomeFeatureEnabled(bool value)
  {
    _isAwesomeFeatureActivated = value;
  }

  public bool IsAwesomeFeatureActivated
  {
    get { return _isAwesomeFeatureActivated; }
  }
}

// with mock object
[Test]
public void ExecuteFeature_WhenNotActivated_DoNothing()
{
  var mockConfig = new MockConfiguration();
  mockConfig.SetIsAwesomeFeatureActivated(false);
  var feature = new AwesomeFeature(mockConfig);
  feature.ExecuteFeature();
  Assert.SomethingHere();
}

// or with Moq framework
[Test]
public void ExecuteFeature_WithActivated_DoSomething()
{
  var mock = new Mock<IConfiguration>();
  mock.Setup(c => c.IsAwesomeFeatureActivated).Returns(true);

  var feature = new AwesomeFeature(mock.Object);
  feature.ExecuteFeature();

  Assert.SomethingHere();
}