c# - MVP、WinForms、单元测试、最小起订量、NUnit : Verify that event handlers have been added to a dependency

Question

我有演示者、 View 和模型。 View 不知道演示者。Presenter 协调一切并仅通过界面了解 View :

public interface ISuspiciousListManagementView
{

    void ShowMessageBox(MessageBoxButtons messageBoxButtons, string message, string caption, EMessageBoxIcons icon);

    void ShowDialog(IWin32Window owner);
    object AllTypesDataSource { get; set; }
    SuspiciousListType SelectedType { get; set; }
    event EventHandler SelectedTypeChanged;
    string FilePath { get; set; }

    bool ShowOnlyActive { get; set; }
    object AllHistoryAvailableTypesDataSource { get; set; }
    SuspiciousFilteredListType SelectedHistoryType { get; set; }
    event EventHandler SelectedHistoryTypeChanged;

    object HistoryDataGridSource { get; set; }

    event EventHandler SelectedShowOnlyActiveChanged;

    ICommand BrowseFileCommand { get; set; }
    ICommand UploadCommand { get; set; }
    ICommand RefreshCommand { get; set; }

}

Presenter 持有方法 Init:

 public async Task Init()
    {
        _view.AllTypesDataSource = Enum.GetValues(typeof(SuspiciousListType));
        _view.AllHistoryAvailableTypesDataSource = Enum.GetValues(typeof(SuspiciousFilteredListType));
        _view.SelectedTypeChanged += OnSelectedTypeChanged;
        _view.SelectedHistoryTypeChanged += OnSelectedHistoryTypeChanged;
        _view.SelectedShowOnlyActiveChanged += OnSelectedShowOnlyActiveChanged;
        _view.HistoryDataGridSource = await GetFilterHistoryItems();
    }

和文件名:

  private readonly ISuspiciousListManagementView _view;

这是通过构造函数注入(inject)的。

我需要验证这些代码行是否已经运行:

    _view.SelectedTypeChanged += OnSelectedTypeChanged;
    _view.SelectedHistoryTypeChanged += OnSelectedHistoryTypeChanged;
    _view.SelectedShowOnlyActiveChanged += OnSelectedShowOnlyActiveChanged;

我想运行这样的东西:

 [Test]
    public async void Presenter_Verify_HistoryDataGridSource_assigned_Test()
    {
        await _presenter.Init();
       _viewMock.Verify(dp => dp.SelectedHistoryTypeChanged != null);//Compilation error
    }

如何测试是否已添加事件处理程序？我的设计有什么问题？

在此先感谢您的帮助。

Answer 1

在“自动”事件的情况下，像这样:

class Test {
    public event Action MyEvent;
}

可以通过反射获取调用列表:

var eventField = test.GetType().GetField(nameof(test.MyEvent), BindingFlags.Instance | BindingFlags.NonPublic);
var eventDelegate = eventField.GetValue(test);
//either get invocation list or just compare eventDelegate with null
var invocationList = eventDelegate != null ? ((Delegate)eventDelegate).GetInvocationList() : new Delegate[0];
bool anySubscribers = invocationList.Length > 0;

那是因为编译器将 MyEvent 扩展为(非常粗略地)如下:

class Test {
    private Action MyEvent;

    public event Action MyEvent
    {
        add { Delegate.Combine(this.MyEvent, (Delegate) value);}
        remove { Delegate.Remove(this.MyEvent, value); }
    }
}

我们可以获得该私有(private)(编译器生成的)字段的值。

如果事件被显式实现:

class Test {        
    public event Action MyEvent
    {
        add
        {
            // do something

        }
        remove
        {
            // do something else                
        }
    }
}

你不能这样做，因为甚至可能不是订阅者的概念 - add 和 remove 可以执行任意操作。但这很可能不是你的情况。