Question

Look at the code snippet:

This is what I normally do when coding against an enum. I have a default escape with an InvalidOperationException (I do not use ArgumentException or one of its derivals because the coding is against a private instance field an not an incoming parameter).

I was wondering if you fellow developers are coding also with this escape in mind….

public enum DrivingState {Neutral, Drive, Parking, Reverse};  public class MyHelper {     private DrivingState drivingState = DrivingState.Neutral;      public void Run()     {         switch (this.drivingState)         {             case DrivingState.Neutral:                 DoNeutral();                 break;             case DrivingState.Drive:                 DoDrive();                 break;             case DrivingState.Parking:                 DoPark();                 break;             case DrivingState.Reverse:                 DoReverse();                 break;             default:                 throw new InvalidOperationException(                     string.Format(CultureInfo.CurrentCulture,                      'Drivestate {0} is an unknown state', this.drivingState));         }     } } 

In code reviews I encounter many implementations with only a break statement in the default escape. It could be an issue over time….

Answer 1

I don’t like this approach because the default case is untestable. This leads to reduced coverage in your unit tests, which while isn’t necessarily the end of the world, annoys obsessive-compulsive me.

I would prefer to simply unit test each case and have an additional assertion that there are only four possible cases. If anyone ever added new enum values, a unit test would break.

Something like

[Test] public void ShouldOnlyHaveFourStates() {     Assert.That(Enum.GetValues( typeof( DrivingState) ).Length == 4, 'Update unit tests for your new DrivingState!!!'); }