resolver.js

const defaultResolver = require('jest-resolve/build/default_resolver').default;
const ScriptTransformer = require('jest-runtime').ScriptTransformer;
const fs = require('fs');

const transform = ScriptTransformer.prototype.transform;

Object.defineProperty(ScriptTransformer.prototype, 'transform', {
  enumerable: false,
  value(file, ...args) {
    if (!fs.existsSync(file)) {
      for (const ext of this._config.moduleFileExtensions) {
        const maybe = `${file}.${ext}`;

        if (fs.existsSync(maybe)) {
          file = maybe;
          break;
        }
      }
    }

    return transform.call(this, file, ...args);
  }
});

module.exports = (...args) => {
  return defaultResolver(...args);
};