JEST 单元测试配置文件说明

最近在做一个 JS + TS 项目，使用 JEST 做测试，我本地的配置文件如下

module.exports = {
  roots: [
    '<rootDir>/test',
  ],
  testRegex: 'test/(.+)\\.test\\.(jsx?|tsx?)$',
  transform: {
    '^.+\\.[jt]sx?$': 'ts-jest',
  },
  moduleFileExtensions: ['ts', 'tsx', 'js', 'jsx', 'json', 'node'],
};

参数简单说明

• roots 测试文件的位置（字符串或者数组）
• testRegex 测试文件匹配的文件格式（正则表达式）这里匹配 .test.jsx .test.tsx 的文件
• transform 转换器（编译器）：是一个对象，key 是正则表达式（满足的文件），值是采用的编译器（转换器）ts-test 这个库
• moduleFileExtensions 这个是支持的文件类型

参数具体说明

roots [array<string>]

Default: ["<rootDir>"]

Jest用于搜索文件的目录的路径列表

A list of paths to directories that Jest should use to search for files in.

There are times where you only want Jest to search in a single sub-directory (such as cases where you have a src/ directory in your repo), but prevent it from accessing the rest of the repo.

Note: While rootDir is mostly used as a token to be re-used in other configuration options, roots is used by the internals of Jest to locate test files and source files. This applies also when searching for manual mocks for modules from node_modules (__mocks__ will need to live in one of the roots).

Note: By default, roots has a single entry <rootDir> but there are cases where you may want to have multiple roots within one project, for example roots: ["<rootDir>/src/", "<rootDir>/tests/"].

testRegex [string | array<string>]

Default: (/__tests__/.*|(\\.|/)(test|spec))\\.[jt]sx?$

Jest用于检测测试文件的模式

The pattern or patterns Jest uses to detect test files.

By default it looks for .js, .jsx, .ts and .tsx files inside of __tests__ folders, as well as any files with a suffix of .test or .spec (e.g. Component.test.js or Component.spec.js). It will also find files called test.js or spec.js. See also [testMatch array], but note that you cannot specify both options.

The following is a visualization of the default regex:

├── __tests__
│   └── component.spec.js # test
│   └── anything # test
├── package.json # not test
├── foo.test.js # test
├── bar.spec.jsx # test
└── component.js # not test

Note: testRegex will try to detect test files using the absolute file path, therefore, having a folder with a name that matches it will run all the files as tests

transform[object<string, pathToTransformer | [pathToTransformer, object]>]

Default: {"\\.[jt]sx?$": "babel-jest"}

A map from regular expressions to paths to transformers. A transformer is a module that provides a synchronous function for transforming source files.

从正则表达式到转换器的路径的映射。 转换器是提供同步功能以转换源文件的模块。例如，如果您希望能够在节点尚不支持的模块或测试中使用新的语言功能，则可以插入许多将JavaScript的未来版本编译为当前版本的编译器之一。

For example, if you wanted to be able to use a new language feature in your modules or tests that aren’t yet supported by node, you might plug in one of many compilers that compile a future version of JavaScript to a current one. Example: see the examples/typescript example or the webpack tutorial.

Examples of such compilers include:

• Babel
• TypeScript
• async-to-gen
• To build your own please visit the Custom Transformer section

You can pass configuration to a transformer like {filePattern: ['path-to-transformer', {options}]} For example, to configure babel-jest for non-default behavior, {"\\.js$": ['babel-jest', {rootMode: "upward"}]}

Note: a transformer is only run once per file unless the file has changed. During the development of a transformer it can be useful to run Jest with --no-cache to frequently delete Jest’s cache.

Note: when adding additional code transformers, this will overwrite the default config and babel-jest is no longer automatically loaded. If you want to use it to compile JavaScript or Typescript, it has to be explicitly defined by adding {"\\.[jt]sx?$": "babel-jest"} to the transform property. See babel-jest plugin

moduleFileExtensions[array<string>]

Default: ["js", "json", "jsx", "ts", "tsx", "node"]

An array of file extensions your modules use. If you require modules without specifying a file extension, these are the extensions Jest will look for, in left-to-right order.

We recommend placing the extensions most commonly used in your project on the left, so if you are using TypeScript, you may want to consider moving “ts” and/or “tsx” to the beginning of the array.

模块使用的文件扩展名数组。 如果您需要模块而未指定文件扩展名，则这些是Jest将按从左到右的顺序查找的扩展名。

我们建议将项目中最常用的扩展名放在左侧，因此，如果您使用的是TypeScript，则可能需要考虑将“ ts”和/或“ tsx”移动到数组的开头。

参考文档

其他的配置可以参考官方文档

https://jestjs.io/docs/en/configuration