如何使用NUnit對事件訂閱進行單元測試

Question

您好，我想知道是否有人知道我的問題的答案：

考慮以下代碼

class TheHandler
{
    ...
    Public EventHandler myRealWorldEvent;
    ...


}

class TheSubscriber
{
    private TheHandler myHandler = new TheHandler();

    public subscribeToHandler()
    { 
        myHandler.myRealWorldEventHandler += OnSomethingHappens;

    }

     ...

    pirvate OnSomeThingHappens()
    {
       ...
    }
}

我的問題是->如何測試（僅使用NUnit）OnSomethingHappens已訂閱myRealWorldEventHandler。 我無法更改SUT /生產代碼，也無法模擬（Moq / Nmock等）。 有人知道我的問題的解決方案嗎？

最好的祝福，

正通

Answer 1

NUnit不會這樣做-測試某些私有處理程序是否訂閱了某個私有字段。 涉及太多私人事務。 但是，有了反射的一點幫助，您便無能為力。 請注意，這不是漂亮的代碼：

var subscriber = new TheSubscriber();
var handlerField = typeof(TheSubscriber)
    .GetFields(BindingFlags.NonPublic | BindingFlags.Instance)
    // if field with such name is not present, let it fail test
    .First(f => f.Name == "myHandler");

var handlerInstance = handlerField.GetValue(subscriber);
var someEventField = typeof(TheHandler)
    .GetFields(BindingFlags.NonPublic | BindingFlags.Instance)
    .First(f => f.Name == "myRealWorldEvent");

var eventInstance = (EventHandler) someEventField.GetValue(handlerInstance);
var subscribedMethod = eventInstance
    .GetInvocationList()
    .FirstOrDefault(d => d.Method.Name == "OnSomethingHappens");

Assert.That(subscribedMethod, Is.Not.Null);

如果您必須處理大量舊系統測試（例如，私有成員，靜態成員-一些免費框架無法很好地處理或根本無法解決的問題 ）-我建議您看一下諸如TypeMock或JustMock之類的工具。

Answer 2

有同樣的問題。 jimmy_keen中的代碼在舊的.NET中無法正常工作。 通過編寫輔助方法解決了它：

public static void assertSubscribed<EventHandlerType>(object handler, object subscriber, string eventName = null) {
    var inappropriate = false;
    try {
        if (!typeof (EventHandlerType).IsSubclassOf(typeof (Delegate)) ||
            typeof (EventHandlerType).GetMethod("Invoke").ReturnType != typeof (void))
            inappropriate = true;
    } catch (AmbiguousMatchException) {
        inappropriate = true;
    } finally {
        if (inappropriate) throw new Exception("Inappropriate Delegate: " + typeof (EventHandlerType).Name);
    }

    var handlerField = subscriber.GetType().GetFields(BindingFlags.NonPublic | BindingFlags.Instance)
        .First(h => h.FieldType.IsInstanceOfType(handler));

    var handlerInstance = handlerField == null ? null : handlerField.GetValue(subscriber);
    var eventField = handlerInstance == null ? null : handlerInstance.GetType().GetFields(BindingFlags.NonPublic | BindingFlags.Instance)
        .First(f => (f.FieldType.IsAssignableFrom(typeof (EventHandlerType)) &&
                     (eventName == null || eventName.Equals(f.Name))));

    var eventInstance = eventField == null ? null : (Delegate)eventField.GetValue(handlerInstance);
    var subscribedMethod = eventInstance == null
        ? null 
        :eventInstance.GetInvocationList().FirstOrDefault(
            d => d.Method.DeclaringType != null && d.Method.DeclaringType.IsInstanceOfType(subscriber));

    Assert.That(subscribedMethod, Is.Not.Null);
}

“不”方法：

public static void assertNotSubscribed<EventHandlerType>(object handler, object subscriber, string eventName = null) {
    var inappropriate = false;
    try {
        if (!typeof (EventHandlerType).IsSubclassOf(typeof (Delegate)) ||
            typeof (EventHandlerType).GetMethod("Invoke").ReturnType != typeof (void))
            inappropriate = true;
    } catch (AmbiguousMatchException) {
        inappropriate = true;
    }
    if (inappropriate) return;

    var handlerField = subscriber.GetType().GetFields(BindingFlags.NonPublic | BindingFlags.Instance)
        .First(h => h.FieldType.IsInstanceOfType(handler));

    var handlerInstance = handlerField == null ? null : handlerField.GetValue(subscriber);

    var eventField = handlerInstance == null ? null : handlerInstance.GetType()
        .GetFields(BindingFlags.NonPublic | BindingFlags.Instance)
        .First(f => (f.FieldType.IsAssignableFrom(typeof (EventHandlerType)) &&
                     (eventName == null || eventName.Equals(f.Name))));

    var eventInstance = eventField==null?null:(Delegate) eventField.GetValue(handlerInstance);
    var subscribedMethod = eventInstance == null
        ? null
        : eventInstance.GetInvocationList().FirstOrDefault(
                d => d.Method.DeclaringType != null && d.Method.DeclaringType.IsInstanceOfType(subscriber));

    Assert.That(subscribedMethod, Is.Null);
}

和調用：

assertSubscribed<EventHandler>(handler, subscriber);
assertNotSubscribed<EventHandler>(handler, subscriber);
assertSubscribed<EventHandler>(handler, subscriber, "myRealWorldEvent");
assertNotSubscribed<EventHandler>(handler, subscriber, "myRealWorldEvent");

不要為代碼樣式約定而煩惱我，但此方法看起來足夠緊湊。