createJestConfig.ts

import { Config } from '@jest/types';

export type JestConfigOptions = Partial<Config.InitialOptions>;

export function createJestConfig(
  _: (relativePath: string) => void,
  rootDir: string
): JestConfigOptions {
  const config: JestConfigOptions = {
    transform: {
      '.(ts|tsx)$': require.resolve('ts-jest/dist'),
      '.(js|jsx)$': require.resolve('babel-jest'), // jest's default
    },
    transformIgnorePatterns: ['[/\\\\]node_modules[/\\\\].+\\.(js|jsx)$'],
    moduleFileExtensions: ['ts', 'tsx', 'js', 'jsx', 'json', 'node'],
    collectCoverageFrom: ['src/**/*.{ts,tsx,js,jsx}'],
    testEnvironment: 'jsdom',
    testEnvironmentOptions: {
      url: 'https://localhost/',
    },
    testMatch: ['<rootDir>/**/*.(spec|test).{ts,tsx,js,jsx}'],
    rootDir,
    watchPlugins: [
      require.resolve('jest-watch-typeahead/filename'),
      require.resolve('jest-watch-typeahead/testname'),
    ],
  };

  return config;
}