CommandMediatorTest.cs

// Fire command and validate mediator
[Test(Description = "Executing DisplayArticlesViewCommand sends message with products articles [Mikael Deurell]")]
 public void Executing_DisplayArticlesViewCommand_SendsDisplayArticleViewListWithProvidedArticles()
 {
     // Given the user wants to display selected articles in a dialogue view
     var sut =
         new ProductViewModel(new Product("1", "desc", ProductType.Assortment, "10", "10", _dummyArticles, null,
                                          0));
     int notify = 0;
     ObservableCollection<ArticleViewModel> articlesReceived = null;
     Messenger.Instance.Register(MessageType.DisplayArticleViewList,
                                 (ObservableCollection<ArticleViewModel> articles) =>
                                     {
                                         articlesReceived = articles;
                                         ++notify;
                                     });

     // When the user clicks button and trigger the execution of a DisplayArticleViewDialogueCommand
     ICommand command = sut.DisplayArticleViewDialogueCommand;
     command.Execute(null);

     // Then the selected articles received to be displayed by the viewmodel are the same as the articles sent to the mediator
     Assert.That(articlesReceived, Is.EqualTo(sut.Articles));
     Assert.That(notify, Is.EqualTo(1));
 }