我试图第一次在打字稿中写一个简单的界面,并对几乎所有事情都有疑虑。
问题很简单。如何描述这个简单的jest matcher扩展?
/**
* @param {*} v Any value
*/
function just (v) {
return {
fmap: f => just(f(v))
}
}
expect.extend({
/** Compare the two values inside two functors with Object.is
* @method
* @augments jest.Matchers
* @param {*} actual The functor you want to test.
* @param {*} expected The functor you expect.
*/
functorToBe(actual, expected) {
const actualValue = getFunctorValue(actual)
const expectedValue = getFunctorValue(expected)
const pass = Object.is(actualValue, expectedValue)
return {
pass,
message () {
return `expected ${actualValue} of ${actual} to ${pass ? '' : 'not'} be ${expectedValue} of ${expected}`
}
}
}
})
test('equational reasoning (identity)', () => {
expect(just(1)).functorToBe(just(1))
})
我试过这个,但根本不确定泛型类型:
import { Matchers } from 'jest'
interface Functor<T> {
(value?: any): {
fmap: (f: value) => Functor<T>
}
}
interface Matchers<R> {
functorToBe(actual: Functor<T>, expected: Functor<T>): R
}
参考:JSDoc document object method extending other class
Matchers<R>
的jest类型定义的要点:
/**
* The `expect` function is used every time you want to test a value.
* You will rarely call `expect` by itself.
*/
interface Expect {
/**
* The `expect` function is used every time you want to test a value.
* You will rarely call `expect` by itself.
*
* @param actual The value to apply matchers against.
*/
<T = any>(actual: T): Matchers<T>;
/**
* You can use `expect.extend` to add your own matchers to Jest.
*/
extend(obj: ExpectExtendMap): void;
// etc.
}
嗯,这很令人困惑。 jest repo中唯一的index.d.ts是https://github.com/facebook/jest/blob/master/packages/jest-editor-support/index.d.ts,但这不是我在vscode中获得的那个,即https://github.com/DefinitelyTyped/DefinitelyTyped/blob/master/types/jest/index.d.ts#L471。
你对Matchers
的合并几乎是正确的,但是通过查看Definitely Typed [1]上的jest类型,我可以看到Matchers
嵌套在jest
命名空间内。包含此内容的Typescript手册的一部分是namespace merging。
namespace jest {
export interface Matchers<R> {
functorToBe<T>(actual: Functor<T>, expected: Functor<T>): R;
}
}
当我测试这个时,我需要一个tsconfig.json来获取我的JS文件以查看声明:
{
"compilerOptions": {
"allowJs": true,
"checkJs": true,
},
"include": [
"test.js",
"extensions.ts",
]
}
jsconfig.json几乎是一回事,但不要求你明确地添加"allowJs": true
。但请注意,添加tsconfig或jsconfig将关闭自定义类型的类型的自动下载,并且您必须手动npm install @types/jest
(以及您使用的库的任何其他类型)。如果您不想添加tsconfig,我可以在JS文件中手动添加引用作为第一行:
/// <reference path="./extensions.ts" />
它应该是这样的:
functorToBe(expected: R): R;
这是让我感到困惑的地方。如果您对问题的这一部分有疑问,请告诉我,我会尽力提供帮助。