How configure Jest when using react-app-rewired and customize-cra?

Question

I am trying set up tests with Jest in a create-react-app that is using the override function from customize-cra and react-app-rewired. I have set up a relative path alias and when I run tests it throwing the error cannot find module

here is the code...

// LoginForm.test.js

import React from 'react';
import { render, fireEvent } from '@testing-library/react';
import LoginForm from './LoginForm';


it('submits', () => {
  const onSubmit = jest.fn();
  const { getByText } = render(<LoginForm onSubmit={onSubmit} />);
  fireEvent.click(getByText('Log in'));
  expect(onSubmit).toHaveBeenCalled();
});

// config-overrides.js

const {
  override,
  fixBabelImports,
  addLessLoader,
  addBabelPlugin
} = require("customize-cra");

module.exports = override(
  fixBabelImports("import", [
    {
      libraryName: "antd",
      libraryDirectory: "es"
      // style: true,
    },
    {
      libraryName: "ant-design-pro",
      libraryDirectory: "lib"
      // style: true,
    }
  ]),

  addBabelPlugin([
    "babel-plugin-root-import",
    {
      rootPathSuffix: "./src"
    }
  ]),

  addLessLoader({
    javascriptEnabled: true,
    modifyVars: {
      "@select-item-selected-font-weight": "500",
      "@font-family":
        '"Futura W01", "Futura", -apple -system, BlinkMacSystemFont, "Segoe UI", sans-serif',
      "@pagination-font-family":
        '"Futura W01", "Futura", -apple -system, BlinkMacSystemFont, "Segoe UI", sans-serif',
      "@statistic-font-family":
        '"Futura W01", "Futura", -apple -system, BlinkMacSystemFont, "Segoe UI", sans-serif'
    }
  })
);

Any pointers much appreciated, thank you.

Answer 1

This is maybe a bit old but I just came across it and solved it so maybe it can help other people.

React app rewired uses react-scripts under the hood so it will not pick up your webpack configuration files. However there is a way to customize it, you can put your jest configuration in the root of your package.json:

"jest": {
    "moduleNameMapper": {
        "^@app(.*)$": "<rootDir>/src/ui/app$1"
    },
    "setupFiles": [
       "<rootDir>/config/jest/setupTests.js"
    ]
}

You can see that react-script is picking up this config if you go to the source code of react-scripts/scripts/test and see that it is creating the jest config:

const createJestConfig = require('./utils/createJestConfig');

And that file overrides the default configuration with the jest config in your package.json:

const overrides = Object.assign({}, require(paths.appPackageJson).jest);

Where paths.appPackageJson is your package.json

Answer 2

As tests don't go via webpack the path aliases won't work. However, they do go through Babel so you can use `babel-plugin-module-resolver'. Normally you'd do it like this:

// .babelrc
{
"plugins": [
  ["module-resolver", {
    "root": ["./src"],
    "alias": {
      "test": "./test",
      "components": "./src/components"
    }
  }]
 ]
}

But looking atoverride above it looks like this might work:

addBabelPlugin([
  "babel-plugin-root-import",
  {
    rootPathSuffix: "./src"
  },
  "module-resolver",{
      "root": ["./src"],
       "alias": {
          "test": "./test",
          "components": "./src/components"
       }
   }
 ])

Answer 3

You can use .babelrc, I made that way

Read the README.md of react-app-rewired , it helped me a lot.

// for jest 
{
    "plugins": [
        [
            "babel-plugin-root-import",
            {
                "rootPathSuffix": "src"
            }
        ]
    ]
}

It for

"babel-plugin-root-import": "~6.4.1" "customize-cra": "~0.9.1" "react": "~16.8.6"