我无法正确配置玩笑以导入模块(setupFilesAfterEnv)

问题描述

我正在使用@angular-builders/jest以便在测试有角度的项目时用笑话代替业力.我想通过2个库来获得更多的笑话匹配器:jest-extended和@testing-library/jest-dom.

I am using @angular-builders/jest in order to replace karma by jest when testing angular projects.There are 2 libraries that I like to get extra matchers for jest: jest-extended and @testing-library/jest-dom.

我找不到自动导入匹配器的方法，因此不必在每个规格文件中导入它们.

I cannot find a way to import automatically the matchers so that I don't have to import them in each spec file.

用于重现jest-extended

minimal example to reproduce the problem with jest-extended

首先，创建一个有角度的项目并安装玩笑依赖项

First, create an angular project and install jest dependencies

ng new --defaults my-project
cd my-project
yarn add -D jest @types/jest @angular-builders/jest jest-extended

然后编辑angular.json替换构建器

...
"test": {
    "builder": "@angular-builders/jest:run"
},

到目前为止，我可以使用带命令的笑话来运行并通过测试

So far, I can run and pass the tests using jest with command

ng test

现在，我使用一个用笑话扩展的匹配器添加一个测试.在app.component.spec.ts:

Now I add a test using one of the jest-extended matchers. In app.component.spec.ts:

...
  it('should work with jest-extended matchers', () => {
    expect([1, 1, 1]).toBeArrayOfSize(3);
  });

尝试#1

创建jest.config.js

module.exports = {
  setupFilesAfterEnv: [
    'jest-extended',
  ],
};

不起作用，出现错误TS2339: Property 'toBeArrayOfSize' does not exist on type 'ArrayLikeMatchers<number>'

尝试#2

使用中间安装文件；创建jest.config.js

use an intermediate setup file; create jest.config.js

module.exports = {
  setupFilesAfterEnv: [
    'my-jest-setup.ts',
  ],
};

与my-jest-setup.ts

import 'jest-extended'

行！测试通过...但是，只要我更改规范文件中的内容

Works! Test passes... BUT as soon as I change something in my spec file

...
  it('should work with jest-extended matchers', () => {
    expect([1, 1, 1]).toBeArrayOfSize(3);
    expect(true).toBeTruthy();
  });

并再次运行测试，我得到与尝试#1相同的错误.我怀疑是缓存问题

and run the test again, I get the same error as in attempt #1. I suspect a cache issue

解决方法

使用尝试#2并在每次运行之前清除jest缓存

Use attempt #2 and clear jest cache before each run with

ng test --clearCache && ng test

我不喜欢这种解决方案，因为当有许多规格文件时，高速缓存旨在加快处理速度，每次清除高速缓存都会产生敏感影响.而且，我认为在观看模式下使用笑话时无法清除缓存

I don't like this solution because the cache is intended to speed up things and clearing the cache each time has a sensitive impact when there are many spec files. Moreover, I don't think it is possible to clear cache when using jest in watch mode

对不起，这有点长，谢谢您的阅读，直到最后

Sorry, this was a bit long, thanks if you read it to the end

推荐答案

我终于找到了我认为正确的解决方案.从最小示例开始，以用笑话扩展，

I finally found what I believe the right solution. Starting from minimal example to reproduce the problem with jest-extended,

1. 创建jest.config.js文件(尝试1终于是一个不错的开始)

1. create jest.config.js file (Attempt 1 was finally a good start)

module.exports = {
  setupFilesAfterEnv: [
    'jest-extended',
  ],
};

1. 编辑tsconfig.spec.json并将"types": ["jasmine", "node"]替换为"types": ["jest", "node", "jest-extended"]

1. edit tsconfig.spec.json and replace "types": ["jasmine", "node"] by "types": ["jest", "node", "jest-extended"]

{
  "extends": "./tsconfig.json",
  "compilerOptions": {
    "outDir": "./out-tsc/spec",
    "types": ["jest", "node", "jest-extended"] // <==== what was missing
  },
  "files": ["src/test.ts", "src/polyfills.ts"],
  "include": ["src/**/*.spec.ts", "src/**/*.d.ts"]
}

和瞧.实际上，这将在编译中包括jest和jest-extended声明文件.现在，我可以获得TypeScript类型检查的所有好处以及缓存的速度提高(显然，首次运行除外).

and voilà. This will actually includes jest and jest-extended declaration files in compilation. I now get all the benefits of TypeScript type checkings and the speed improvements of the cache (except for first run, obviously).

我希望这对您有帮助

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