Basic setupSandboxGlobal sandboxCI setupAssertionsSee alsoLet's say we have a small Node program and want to confirm it logs "Hello" string to the consoleapp.js12345const app = () => console.log('Hello')module.exports = { app }if (!module.parent) { app()}1234$ npm start> node ./appHelloWe need a test runner to write a test and an ability to spy console.log method. We could write both the test runner and method spying ourselves, but there are already 2 great tools for this: Mocha.js and Sinon.js...