Testing with Jest and Webpack aliases

Question

I am looking to be able to use webpack aliases to resolve imports when using jest, and optimally, reference the webpack.aliases to avoid duplication.

Je

Answer 1

Using: "jest": "^26.5.3", and "webpack": "4.41.5", I was able to properly match my webpack/typescript aliases in the jest.config.js with this pattern:

Webpack config:

module.exports = {
   // the rest of your config
    resolve: {
      alias: {
        'components': path.resolve(__dirname, 'js/app/components'),
        'modules': path.resolve(__dirname, 'js/app/modules'),
        'types': path.resolve(__dirname, 'js/types'),
        'hooks': path.resolve(__dirname, 'js/app/hooks'),
        'reducers': path.resolve(__dirname, 'js/app/reducers'),
        '__test-utils__': path.resolve(__dirname, 'js/app/__test-utils__') 
      }
    },
}

Jest.config.js:

  moduleNameMapper: {
    '^types/(.*)$':  '/js/types/$1',
    '^components/(.*)$': '/js/app/components/$1',
    '^modules/(.*)$':  '/js/app/modules/$1',
    '^hooks/(.*)$':  '/js/app/hooks/$1',
    '^reducers/(.*)$':  '/js/app/reducers/$1',
    '^__test-utils__/(.)$': '/js/app/__test-utils__/$1' 
  }

Here's an explanation of the symbols:

• (.*)$: capture whatever comes after the exact match (the directory)
• $1: map it to this value in the directory I specify.

and tsconfig.json:

    "paths": {
      "config": ["config/dev", "config/production"],
      "components/*": ["js/app/components/*"],
      "modules/*": ["js/app/modules/*"],
      "types/*": ["js/types/*"],
      "hooks/*": ["js/app/hooks/*"],
      "reducers/*": ["js/app/reducers/*"],
      "__test-utils__/*": ["js/app/__test-utils__/*"]
    }