要模拟对象，是否必须实现接口或将其标记为虚拟? [英] To mock an object, does it have to be either implementing an interface or marked virtual?

问题描述

还是该类也可以实现抽象类?

or can the class be implementing an abstract class also?

推荐答案

要模拟类型，它必须是接口(也称为 pure virtual )或具有虚拟成员(抽象成员也是虚拟的.

To mock a type, it must either be an interface (this is also called being pure virtual) or have virtual members (abstract members are also virtual).

通过此定义，您可以模拟虚拟的所有内容.

By this definition, you can mock everything which is virtual.

本质上，动态模拟不会做您无法手工完成的任何事情.

假设您正在针对此类接口进行编程:

Let's say you are programming against an interface such as this one:

public interface IMyInterface
{
    string Foo(string s);
}

您可以手动创建IMyInterface的特定于测试的实现，该实现将忽略输入参数并始终返回相同的输出:

You could manually create a test-specific implementation of IMyInterface that ignores the input parameter and always returns the same output:

public class MyClass : IMyInterface
{
    public string Foo(string s)
    {
        return "Bar";
    }
}

但是，如果您要测试使用者对不同返回值的反应方式，那么该操作很快就会重复出现，因此您可以使用一个框架来动态创建它们，而不用手动编写 Test Doubles 为你.

However, that becomes repetitive really fast if you want to test how the consumer responds to different return values, so instead of coding up your Test Doubles by hand, you can have a framework dynamically create them for you.

想象一下，动态模拟实际上编写的代码类似于上面的MyClass实现(它们实际上并没有编写代码，而是动态地发出类型，但这是一个足够准确的类比).

Imagine that dynamic mocks really write code similar to the MyClass implementation above (they don't actually write the code, they dynamically emit the types, but it's an accurate enough analogy).

在这里，您可以使用Moq定义与MyClass相同的行为:

Here's how you could define the same behavior as MyClass with Moq:

var mock = new Mock<IMyInterface>();
mock.Setup(x => x.Foo(It.IsAny<string>())).Returns("Bar");

在两种情况下，创建对象时都会调用所创建类的构造函数.由于接口没有构造函数，因此通常是默认的构造函数(分别是MyClass和动态发出的类).

In both cases, the construcor of the created class will be called when the object is created. As an interface has no constructor, this will normally be the default constructor (of MyClass and the dynamically emitted class, respectively).

您可以对像这样的具体类型做同样的事情:

You can do the same with concrete types such as this one:

public class MyBase
{
    public virtual string Ploeh()
    {
        return "Fnaah";
    }
}

通过手工，您将能够从MyBase派生并重写Ploeh方法，因为它是虚拟的:

By hand, you would be able to derive from MyBase and override the Ploeh method because it's virtual:

public class TestSpecificChild : MyBase
{
    public override string Ploeh()
    {
        return "Ndøh";
    }
}

动态模拟库可以做到这一点，抽象方法也是如此.

A dynamic mock library can do the same, and the same is true for abstract methods.

但是，您不能编写覆盖非虚拟或内部成员的代码，动态模拟也不能.他们只能做您可以手工做的事情.

However, you can't write code that overrides a non-virtual or internal member, and neither can dynamic mocks. They can only do what you can do by hand.

注意:上面的描述对于大多数动态模拟都是正确的，但TypeMock除外，它是不同的，而且...令人恐惧.

Caveat: The above description is true for most dynamic mocks with the exception of TypeMock, which is different and... scary.

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