allows imports in jest tests to not be confused by webpack imports of non-javascript files

jest.config.js

// HOW TO:
// jest --config jest.config.js

// -- assetsTransformer.js --
// const path = require('path');
// module.exports = {
//   process(src, filename, config, options) {
//     return 'module.exports = ' + JSON.stringify(path.basename(filename)) + ';';
//   },
// };

// -- jest.config.js --
module.exports = {
  verbose: true,
  // This helps prevent configure Jest to gracefully handle asset files such as stylesheets and images. 
  // Usually, these files aren't particularly useful in tests so we can safely mock them out.
  // https://jestjs.io/docs/en/webpack
  moduleNameMapper: {
    "\\.(jpg|jpeg|png|gif|eot|otf|webp|svg|ttf|woff|woff2|mp4|webm|wav|mp3|m4a|aac|oga)$": "<rootDir>/assetsTransformer.js",
    "\\.(css|less)$": "<rootDir>/assetsTransformer.js"
  }
}