Typescript - 具有映射类型的模拟接口 [英] Typescript - Mock interface with mapped types

问题描述

出于测试目的，我希望能够创建一个实现接口的对象，仅使用我测试所需的功能，而无需手动维护具有所有可能属性的模拟对象.通常，我一次只使用一个函数，因此不需要定义所有其他函数，但我不希望 TS 一直抱怨缺少属性.

For testing purpose, I'd like to be able to create an object implementing an interface, only with function I need for my test, without having to manually maintain a mock object with all possible properties. Generally, I'm using one function at a time, so don't need to define all others but I don't want TS to keep complaining about missing properties.

例如，我有一个接口 IFoo :

For example, I have an interface IFoo :

interface IFoo {
    myFunc(): string;
    otherFunc(): number;
}

我尝试创建一个映射类型，它将 jest.Mock<{}> 分配给 IFoo

I tried to create a mapped type, which assign jest.Mock<{}> to all properties of IFoo

type Mockify<T> = {
    [P in keyof T]: jest.Mock<{}>
};

这样称呼:

const mockFoo: Mockify<IFoo> = {
    otherFunc: {
        // Mocked function behavior
    }
}

这种方法的问题是 TS 抱怨传递给 Mockify 的对象缺少 myFunc 属性.

The problem with this approach is that TS complains about the missing myFunc property on the object passed to Mockify.

我也尝试过 Mockify> 来忽略缺少的属性，但是我的类型定义与 IFoo 和其他一些依赖于 IFoo 在抱怨.我也可以将所有属性定义为 optionnal，但从概念上讲我不喜欢那样.

I also tried Mockify<Partial<IFoo>> to ignore missing properties, but then my type defintion is different from IFoo and some other functions depending of IFoo are complaining. I could also define all properties as optionnal, but conceptually I don't like that.

我感觉映射类型可以胜任这项工作，但我可能没有正确的方法.

I have the feeling that mapped types could make the job, but I maybe don't have the right approach.

感谢您的帮助！

推荐答案

我可以在我的映射类型定义中设置所有属性可选:

I can make all properties optionnal in my mapped type definition:

type Mockify<T> = {
    [P in keyof T]?: jest.Mock<{}>
};

这相当于每次使用 Mockify 时都使用 Partial.

This is equivalent to use Partial everytime I use Mockify.

然后，当稍后使用我的模拟对象时，类型断言将其转换回原始界面，每个人都很高兴

Then, when using my mockified object later on, type assertion casts it back to the original interface and everybody's happy

const mockFoo: Mockify<IFoo> = {
    otherFunc: {
        // Mocked function behavior
    }
} 

dependentFunc(mockFoo as IFoo);

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