config-overrides.js

const fs = require('fs')
const path = require('path')
const traverse = require('traverse')

const setupTestsFile = fs.existsSync(
  path.resolve(__dirname, 'src/setupTests.ts')
)
  ? '<rootDir>/src/setupTests.ts'
  : undefined

module.exports = {
  webpack: (config, env) =>
    Object.assign(
      traverse(config).forEach(function f(x) {
        if (
          x &&
          x.enforce === 'pre' &&
          x.use &&
          x.use instanceof Array &&
          x.use[0] &&
          x.use[0].options &&
          x.use[0].options instanceof Object &&
          x.use[0].options.useEslintrc === false
        ) {
          this.update(
            {
              test: /\.(js|jsx|mjs)$/,
              loader: require.resolve('source-map-loader'),
              enforce: 'pre',
              include: __dirname,
              exclude: /node_modules/
            },
            true
          )
        }
      }),
      {
        devtool:
          process.env.NODE_ENV === 'production'
            ? undefined
            : 'inline-source-map'
      }
    ),
  jest: (config, env) =>
    Object.assign(config, {
      collectCoverageFrom: ['<rootDir>/**/*.{ts,tsx}'],
      setupFiles: [
        path.resolve(
          __dirname,
          'node_modules/react-scripts/config/polyfills.js'
        )
      ],
      setupTestFrameworkScriptFile: setupTestsFile,
      testMatch: [
        '<rootDir>/**/__tests__/**/*.ts?(x)',
        '<rootDir>/**/?(*.)(spec|test).ts?(x)'
      ],
      transform: {
        '^.+\\.(js|jsx|mjs)$': '<rootDir>/node_modules/babel-jest',
        '^.+\\.tsx?$': '<rootDir>/node_modules/ts-jest',
        '^.+\\.css$':
          '<rootDir>/node_modules/react-scripts/config/jest/cssTransform.js',
        '^(?!.*\\.(js|jsx|mjs|css|json)$)':
          '<rootDir>/node_modules/react-scripts/config/jest/fileTransform.js'
      },
      transformIgnorePatterns: [
        '[/\\\\]node_modules[/\\\\].+\\.(js|jsx|mjs|ts|tsx)$'
      ],
      moduleFileExtensions: [
        'web.ts',
        'ts',
        'web.tsx',
        'tsx',
        'web.js',
        'js',
        'web.jsx',
        'jsx',
        'json',
        'node',
        'mjs'
      ],
      globals: {
        'ts-jest': {
          tsConfigFile: 'tsconfig.test.json'
        }
      }
    })
}