The following is an example of a StubSpeakerContactServiceError in C#. You'll note that, when MessageSpeaker is called then a new UnableToContactSpeakerException error is thrown.

class StubSpeakerContactServiceError : ISpeakerContactService
{
  public void MessageSpeaker(string message) 
  {
    throw new UnableToContactSpeakerException();
  } 
}