test.js

 import test from 'ava';

 import uniqueString from 'unique-string';

 import isUp from '.';

 test('up', async t => {

  t.true(await isUp('https://google.com'));

 });

 test('down', async t => {

  t.false(await isUp(`https://foobar${uniqueString()}.com`));

 });

 test('invalid domain', async t => {

  await t.throwsAsync(isUp('unicorn'), 'Invalid URL: unicorn');

 });