Basic JS testing with Jest

.babelrc.js

// Copyright (c) 2014-present, Facebook, Inc. All rights reserved.

module.exports = {
  presets: ["@babel/preset-env"]
};

index.js

export const hello = (name) => `hello ${name}`;

index.test.js

import { hello } from "./index";

describe("works", () => {
  it("welcomes you", () => {
    expect(hello('Paul')).toEqual('hello Paul');
  });
});

package.json

{
  "private": true,
  "version": "0.0.0",
  "name": "getting-started-with-jest",
  "devDependencies": {
    "@babel/core": "*",
    "@babel/preset-env": "*",
    "babel-jest": "*",
    "jest": "*"
  },
  "scripts": {
    "test": "jest"
  }
}