DetailLoaderProgressTest.cs

public class DetailLoaderProgressTest
{
    private List<Fake> _batch;
    private IDetailLoader<Fake> _detailLoader;
    private int _counter;

    public DetailLoaderProgressTest()
    {
        _batch = new List<Fake>();
        _detailLoader = new FakeDetailLoader();
        _counter = 0;
    }

    [Fact]
    public void loader_should_load_items()
    {
        // Original
        _detailLoader.Load(string.Empty, _batch.Add);
        
        Assert.True(_batch.Any());
    }

    [Fact]
    public void loader_should_load_10_items()
    {
        // Original
        _detailLoader.Load(string.Empty, _batch.Add);
        
        Assert.Equal(10, _batch.Count);
    }

    [Fact]
    public void loader_with_decorator_should_load_items()
    {
        // Original
        var progressItem = new ProgressItem();
        progressItem.Start(10);
        var decoratedLoader = new DetailLoaderWithProgressItem<Fake>(_detailLoader, progressItem);

        decoratedLoader.Load(string.Empty, _batch.Add);

        Assert.True(_batch.Any());
    }

    [Fact]
    public void loader_with_decorator_should_load_10_items()
    {
        // Original
        var progressItem = new ProgressItem();
        progressItem.Start(10);
        var decoratedLoader = new DetailLoaderWithProgressItem<Fake>(_detailLoader, progressItem);

        decoratedLoader.Load(string.Empty, _batch.Add);

        Assert.Equal(10, _batch.Count);
    }

    [Fact]
    public void loader_with_decorator_should_report_10_events()
    {
        // Important, but missed this one!
        var progressItem = new ProgressItem();
        progressItem.Start(10);
        var decoratedLoader = new DetailLoaderWithProgressItem<Fake>(_detailLoader, progressItem);

        progressItem.PropertyChanged += OnProgressItemChanged;
        decoratedLoader.Load(string.Empty, _batch.Add);

        Assert.Equal(10, _counter);

        progressItem.PropertyChanged -= OnProgressItemChanged;
    }

    void OnProgressItemChanged(object sender, PropertyChangedEventArgs e)
    {
        _counter++;
    }
}