jest-alias-preprocessor

jest-alias-preprocessor

This package allows you to use aliases when testing with Jest. It's very handy when you want to use your existing webpack configuration, but you can also use it on its own.

Really, it's just a very simple wrapper on top of transform-jest-deps.

Usage

jest-alias-preprocessor exports a higher-order function; to make it work, you have to provide a configuration object for it to use. Simply create a new file, import this module, and either import webpack.config.js, or create a new object from scratch. Then, invoke the function, passing the config as an argument. Finally, link to the preprocessor from your Jest configuration using the scriptPreprocessor option.

Note that your config has to look like a webpack config object even if you don't use webpack. It needs a resolve property, and that property needs to have a root and alias property. You can see how it looks below.

Example 1 ― everything in root directory

const config = require('./webpack.config.js');

module.exports = require('jest-alias-preprocessor')(config);

Example 2 ― no Webpack config

module.exports = require('jest-alias-preprocessor')({
  resolve: {
    root: process.cwd(),
    alias: {
      _js: './app/js',
      _utils: './app/js/utils',
    },
  },
});

Example 3 ― with babel-jest

var config = require('./webpack.config.js');
var aliasPreprocessor = require('jest-alias-preprocessor')(config);
var babel = require('babel-jest');

module.exports = {
  process: function(src, path) {
    src = aliasPreprocessor.process(src, path);
    src = babel.process(src, path);

    return src;
  },
};