Showing how to handle thrown errors in Jest when testing asynchronous code

async.js

async function wontThrowErr() {
  return 'ok';
}

async function mightThrowErr() {
  throw new Error('oops');
}

module.exports = {
  mightThrowErr,
  wontThrowErr,
};

async.test.js

/* Based on: https://jestjs.io/docs/asynchronous#resolves--rejects */

const { mightThrowErr, wontThrowErr } = require('./async');

test('async error should be thrown', () => {
  expect(mightThrowErr()).rejects.toThrow(Error('oops'));
});

test('async error should not be thrown', () => {
  expect(wontThrowErr()).resolves.not.toThrow();
});