WPF中如何对附加属性进行单元测试

Question

WPF中如何对附加属性进行单元测试

7

我仍在学习关于附加行为的知识，并且不知道如何编写一个单元测试。

下面是来自Sacha Barber的Cinch框架的代码，可以通过附加行为关闭窗口。有人能给我展示一个例子单元测试吗？

谢谢！
Berryl

    #region Close

    /// <summary>Dependency property which holds the ICommand for the Close event</summary>
    public static readonly DependencyProperty CloseProperty =
        DependencyProperty.RegisterAttached("Close",
            typeof(ICommand), typeof(Lifetime),
                new UIPropertyMetadata(null, OnCloseEventInfoChanged));

    /// <summary>Attached Property getter to retrieve the CloseProperty ICommand</summary>
    public static ICommand GetClose(DependencyObject source)
    {
        return (ICommand)source.GetValue(CloseProperty);
    }

    /// <summary>Attached Property setter to change the CloseProperty ICommand</summary>
    public static void SetClose(DependencyObject source, ICommand command)
    {
        source.SetValue(CloseProperty, command);
    }

    /// <summary>This is the property changed handler for the Close property.</summary>
    private static void OnCloseEventInfoChanged(DependencyObject sender, DependencyPropertyChangedEventArgs e)
    {
        var win = sender as Window;
        if (win == null) return;

        win.Closing -= OnWindowClosing;
        win.Closed -= OnWindowClosed;

        if (e.NewValue == null) return;

        win.Closing += OnWindowClosing;
        win.Closed += OnWindowClosed;
    }

    /// <summary>
    /// This method is invoked when the Window.Closing event is raised.  
    /// It checks with the ICommand.CanExecute handler
    /// and cancels the event if the handler returns false.
    /// </summary>
    private static void OnWindowClosing(object sender, CancelEventArgs e)
    {
        var dpo = (DependencyObject)sender;
        var ic = GetClose(dpo);
        if (ic == null) return;

        e.Cancel = !ic.CanExecute(GetCommandParameter(dpo));
    }

    /// <summary>
    /// This method is invoked when the Window.Closed event is raised.  
    /// It executes the ICommand.Execute handler.
    /// </summary>
    static void OnWindowClosed(object sender, EventArgs e)
    {
        var dpo = (DependencyObject)sender;
        var ic = GetClose(dpo);
        if (ic == null) return;

        ic.Execute(GetCommandParameter(dpo));
    }

    #endregion

- Berryl

2个回答

3

对于我来说，DependencyProperty的更改和值强制执行本身就像是“不可能的依赖项”。这里还涉及到对Window的引用，使事情变得更加棘手。我认为我会采用谦虚对象模式...

- Anvaka

我实际上可以接受这种情况下的窗口，但那是一个有趣的链接。你能说明在这种情况下如何应用“谦虚对象模式”吗？干杯 - Berryl

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可以查看英文原文，
原文链接

- Joel B Fant · Accepted Answer

你可能会在使用DelegateCommand或者RelayCommand的时候，在你的ICommand中使用lambda表达式。这些实现在各个地方都有，并且Cinch可能也有类似的东西。这里提供一个非常简单的版本（作为示例，不适用于生产环境）：

public class DelegateCommand : ICommand {
    private Action _execute = null;

    public void Execute( object parameter ) {
        _execute();
    }

    public DelegateCommand( Action execute ) {
        _execute = execute;
    }

    #region stuff that doesn't affect functionality
    public bool CanExecute( object parameter ) {
        return true;
    }
    public event EventHandler CanExecuteChanged {
        add { }
        remove { }
    }
    #endregion
}

那么您的测试主体可能看起来像这样：

bool wascalled = false;

var execute = new DelegateCommand(
    () => {
        wascalled = true;
    } );

var window = new Window();
SomeClass.SetClose( window, execute );

// does the window need to be shown for Close() to work? Nope.

window.Close();

AssertIsTrue( wascalled );

这只是一个过于简化的例子。当然，您可能需要执行其他测试，在这种情况下，您应该创建或查找更完整的DelegateCommand实现，该实现还正确地实现了CanExecute等其他功能。