Jest + Typescript. Resolve tsconfig.json paths.

jest.config.js

/**
 * Converts paths defined in tsconfig.json to the format of
 * moduleNameMapper in jest.config.js.
 *
 * For example, {'@alias/*': [ 'path/to/alias/*' ]}
 * Becomes {'@alias/(.*)': [ '<rootDir>/path/to/alias/$1' ]}
 *
 * @param {string} srcPath
 * @param {string} tsconfigPath
 */
function makeModuleNameMapper(srcPath, tsconfigPath) {
    // Get paths from tsconfig
    const {paths} = require(tsconfigPath).compilerOptions;

    const aliases = {};

    // Iterate over paths and convert them into moduleNameMapper format
    Object.keys(paths).forEach((item) => {
        const key = item.replace('/*', '/(.*)');
        const path = paths[item][0].replace('/*', '/$1');
        aliases[key] = srcPath + '/' + path;
    });
    return aliases;
}

const TS_CONFIG_PATH = './tsconfig.json';
const SRC_PATH = '<rootDir>/src';

module.exports = {
    'roots': [
        SRC_PATH
    ],
    'transform': {
        '^.+\\.tsx?$': 'ts-jest'
    },
    'moduleNameMapper': makeModuleNameMapper(SRC_PATH, TS_CONFIG_PATH)
};