How to test ECMAScript modules using Node.js

Install esm-runner.

$ npm install --save-dev esm-runner

Typical ESM test file example.

import TestRunner from 'test-runner'
import assert from 'assert'
import fetch from 'node-fetch'

const tom = new TestRunner.Tom()

tom.test('Math.random() should return a number between 0 and 1', function () {
  const result = Math.random()
  assert.equal(typeof result, 'number')
  assert.ok(result >= 0 && result <= 1)
})

tom.test('REST API should return the current todo item', async function () {
  const response = await fetch('https://jsonplaceholder.typicode.com/todos/1')
  const todo = await response.json()
  assert.equal(todo.userId, 1)
  assert.equal(todo.title, 'delectus aut autem')
})

export default tom

Run the tests using esm-runner. This runner is identical to test-runner with the one difference that it supports ECMAScript Modules (ESM).

$ npx esm-runner test.mjs

Start: 2 tests loaded

✓ synopsis Math.random() should return a number between 0 and 1
✓ synopsis REST API should return the current todo item

Completed in 199ms. Pass: 2, fail: 0, skip: 0.