Question

For example I have SomeClass class which implements ISomeInterface interface with two properties Prop1 and Prop2 (Prop1 has NO setter!!! and Prop2 depends of Prop1):

public class SomeClass : ISomeInterface
    {
        private readonly NameValueCollection settings = ConfigurationManager.AppSettings;
        private readonly string p1;
        private string p2;

        public string Prop1 { get { return settings["SomeSetting"]; } }
        public string Prop2
        {
            get
            {
                switch(Prop1)
                {
                    case "setting1": return "one";
                    case "setting2": return "two";
                    case "setting3": return "three";
                    default: return "one";
                }
            }
            set { p2 = value; }
        }
    }

I need to write unit tests for this class. I suggest they should look like:

[TestMethod]
public void Prop2ShouldReturnOneValueIfSomeSettingEqualsSetting1()
{
    var someClass = new SomeClass();
    Assert.Areequals(someClass.Prop2, "one");
}

[TestMethod]
public void Prop2ShouldReturnTwoValueIfSomeSettingEqualsSetting2()
{
    var someClass = new SomeClass();
    Assert.Areequals(someClass.Prop2, "two");
}

So my question is: How can I force Prop1 return setting1, setting2 etc. if it has no setter? I cannot set the values I need to fields because they are private. Should I mock ISomeInterface or ConfigurationManager??? If so, how can I mock ConfigurationManager if it has no interface??? Should I mock directly ConfigurationManager class??? Will it be right??? Also I don’t understand how can I mock ISomeInterface. I need to test prop2 which depends on prop1. If I type:

[TestMethod]
public void Prop2ShouldReturnTwoValueIfSomeSettingEqualsSetting2()
    {
        var moqSettings = new Mock<ISomeInterface>();
        moqSettings.Setup(p => p.Prop1).Returns("setting2");

        ...
    }

it will not change anything, because moqSettings.Object.Prop2 will be null. And, I’m not sure, but I think it’s wrong to do like that))) So how can I test all cases in prop2???

P.S. For mocking I use Moq.
P.P.S. Sorry for my English))) I hope I explained clearly what i need…

Answer 1

I think your class has several responsibilities – reading configuration, and generating some values depending on configuration settings. If you split those responsibilities, then you can mock your application settings. Create some interface like ISomeConfiguration

public interface ISomeConfiguration
{
    string SomeSetting { get; }
}

Implement it this way:

public class MyConfiguration : ISomeConfiguration
{
    readonly NameValueCollection settings = ConfigurationManager.AppSettings;

    public string SomeSettings
    {
        get { return settings["SomeSetting"]; }
    }
}

And inject this interface to your SomeClass:

public class SomeClass : ISomeInterface
{
   private readonly string p1;
   private string p2;
   private ISomeConfiguration config;

   public SomeClass(ISomeConfiguration config)
   {
       this.config = config;
   }

   public string Prop1 { get { return config.SomeSetting; } }
   public string Prop2
   {
       get
       {
          switch(Prop1)
          {
              case "setting1": return "one";
              case "setting2": return "two";
              case "setting3": return "three";
              default: return "one";
          }
       }
       set { p2 = value; }
  }

}

Now you can mock your configuration without problems:

[TestMethod]
public void Prop2ShouldReturnTwoValueIfSomeSettingEqualsSetting2()
{
    var moqConfig = new Mock<ISomeConfiguration>();
    moqConfig.Setup(p => p.SomeSetting).Returns("setting2");
    var sut = new SomeClass(moqConfig.Object);
    Assert.That(sut.Prop2, Is.EqualTo("two"));
}