起订量It.Is<>不匹配 [英] Moq It.Is<> not matching

问题描述

此代码：

hub.MockedUserRepository.Setup(r => r.Update(It.IsAny<ControllUser>()))
                        .Callback((ControllUser usr) => Console.WriteLine("NULL = " + (usr.Zombies[0].ConnectionId == null)))
                        .Verifiable();

将打印

Will print

NULL = TRUE

NULL = True

，所以我用这个匹配会抓住它想：

So i am thinking using this matching will catch it:

var zombieDisconnectParameterMatcher = It.Is<ControllUser>(x => x.Zombies[0].ConnectionId == null);
hub.MockedUserRepository.Setup(r => r.Update(zombieDisconnectParameterMatcher))
                        .Callback((ControllUser usr) => Console.WriteLine("NULL = " + (usr.Zombies[0].ConnectionId == null)))
                        .Verifiable();

但事实并非如此。

But it does not.

为什么？

推荐答案

通过查看的源据 ，它与表达式树做的。我喜欢的问题;他们可以是相当令人费解。如果您将在下面的方法定义来看一看：

By looking at the source code of It, it has to do with expression trees. I like the question; they can be quite puzzling. If you would take a look at the following method definitions:

public static TValue It.Is<TValue>(Expression<Func<TValue, bool>> match)
{
        return Match<TValue>.Create(
                value => match.Compile().Invoke(value),
                () => It.Is<TValue>(match));
}

public static T Match.Create<T>(Predicate<T> condition, Expression<Func<T>> renderExpression)
{
        // ...
        return default(T);
}

如果您将执行以下命令行：

If you would execute the following line:

var zombieDisconnectParameterMatcher = It.Is<ControllUser>(x => x.Zombies[0].ConnectionId == null);

然后 It.Is< >将尝试调用一个名为 Match.Create<方法ControllUser>（），返回 ControllUser 的默认值。我假设 ControllUser 是一类，因此 zombieDisconnectParameterMatcher 将空。你应该能够看到这个与调试。那么究竟是什么你打电话是：

Then It.Is<ControllUser>() will try to call a method called Match.Create<ControllUser>(), which returns the default of ControllUser. I assume ControllUser is a class and therefore zombieDisconnectParameterMatcher will be null. You should be able to see this with the debugger. So what actually you're calling is:

hub.MockedUserRepository.Setup(r => r.Update(null))
    .Callback((ControllUser usr) => Console.WriteLine("NULL = " + (usr.Zombies[0].ConnectionId == null)))
    .Verifiable();

与非执行更新方法时-null ControllUser ，回调不会触发。因为它不是空不匹配的标准。你也看到验证失败。

When executing the Update method with a non-null ControllUser, the callback will not trigger. It doesn't match the criteria since it's not null. Also you would see the verification fail.

要解决此问题，无论是内联 zombieDisconnectParameterMatcher 变量，或使其一个表达式类型的变量（如表达式来; FUNC。< ...>> ）。使得它保持一个表达和将不被执行，但将通过模拟而不是进行评价。

To resolve this issue, either inline the zombieDisconnectParameterMatcher variable, or make it an expression typed variable (eg. Expression<Func<...>>). So that it stays an expression and will not be executed, but will be evaluated by the mock instead.

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