Now that I have added the close button to the view, the application startup and closing is complete. Now I can start working on the song list, that is, what the current story is all about.
To start with, before adding any songs, the song list should be empty. This ought to be simple to accomplish since, when adding the list to the user interface, it will indeed be initially empty. However, that is just coincidence, so I would of course like to add a test that makes sure it is.
[Test] public void Song_list_is_initially_empty() { Application .Start(view => { Assert.That(view.Songs, Is.Empty); view.ClickCloseButton(); }); }The view has got a property that contains the songs that are displayed. The test makes sure that this property contains an empty list.
I add the property to the SongsViewFake and let it be of the type ReadOnlyCollection<Song>.
public class SongsViewFake : ISongsView { public ReadOnlyCollection<Song> Songs { get; set; } // ... } public class Song { }The reason I use a ReadOnlyCollection<> collection type is that I don't expect the view to modify the list of Songs. Using this type is a way to avoid accidents as well as a documentation for the future readers of the code to understand what is expected.
However, ReadOnlyCollection<> is not as read-only as it appears. It is fully possible for the view to make modifications to a contained item, that is, to a Song. There are ways to prevent this kind of misuse, for instance, by making copies of each Song that the collection holds on to. Then the view can modify its items without affecting other code holding on to the same information.
I will later use a similar approach that will solve this when I discover that the Song class is suboptimal to use here. But more about that later.
The code compiles, so I run the tests.
The test failed as expected, but the message is not the most informative. It appears that since Is.Empty can be used for so many things, NUnit doesn't have enough information to give a good error message. So I change the assertion to the following.
Assert.That(view.Songs, Is.EqualTo(Enumerable.Empty<Song>()));And the failure message is much better.
Just like when adding the event for the close button, I need to add the Songs property to the ISongsView interface and also to the implementing class SongsView.
public interface ISongsView { ReadOnlyCollection<Song> Songs { set; } // ... } public partial class SongsView : Form, ISongsView { // ... public ReadOnlyCollection<Song> Songs { set { _songs.DataSource = value; } } }I only include the setter for the property in the interface since there is no need for getting the property value from the view.
The test is still red, for the same reason, so I add the code necessary to make the test pass.
public class Thingy : ApplicationContext { // ... public void ShowView() { View.OnViewClosed += () => CloseAction( this ); View.Songs = new ReadOnlyCollection<Song>( new List<Song>()); View.OnCloseButtonClick += View.CloseView; View.ShowView(); } }Again, only one line of code is enough to make the test pass. Running the application also works fine.
I check in the code.