Linq .FirstOrDefault()在模拟列表上 [英] Linq .FirstOrDefault() on a Mocked List

问题描述

我正在尝试使用Moq编写一些代码的单元测试，并在我对firstOrDefault()的调用上遇到NullReferenceException.这是我受影响的代码的一个片段:

I'm trying to write a unit test using Moq for some code and coming up against a NullReferenceException on my call to firstOrDefault(). Here is a snippet of my affected code:

    [TestMethod]
    public void LinqAlist()
    {
        var _mockList = new Mock<List<int>>();
        var realData = new List<int>() {1, 2, 3};

        _mockList.Object.AddRange(realData);
        //returns 1
         var realOne = realData.FirstOrDefault(x => x == 1);
        //throws NullReferenceException
        var mockOne = _mockList.Object.FirstOrDefault(x => x == 1);

    }

据我所知，我看不到为什么我得到了Null引用，我已经正确地实例化了它.

I can't see why I'm getting the Null reference, as far as I can tell, I've instantiated it properly.

感谢您的帮助！

我为什么要嘲笑列表?

我试图模拟从List继承的Class的行为，如下所示:

I am attempting to mock the behaviour of a Class which inherits from List as follows:

public class IndxList<T> : List<T>.....

public class ClassUnderTest<T> : IndxList<T>....

我正在尝试调试导致List类为空的原因.

I'm trying to debug down to the cause of my null to the List class.

推荐答案

在模拟类时，您必须格外小心，因为还有更多陷阱. 您无法使用此框架模拟非虚拟方法，即使与其他框架一起使用，基本方法仍将执行.

You have to be carefull when you mock a class as there are some more traps. You cannot mock an non virtual method with this framework and even with others the base method will still be executed.

当模拟一个类型时，它应该是关于简化测试另一部分所需的依赖关系.另外，您只测试单元测试所要涉及的特定部分.

When you mock a type it should be about simplifying the dependencies needed to test an other part. Also that you only test the specific part which the unit test is about.

有了列表，创建一个列表会更容易.您可以假定该类已经过测试并且可以正常工作.

With a list it is easier to just create one. You can assume that this class is tested and working.

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