test.js

 import test from 'ava';

 import fn from './';

 test('up', async t => {

  t.true(await fn('google.com'));

 });

 test('down', async t => {

  t.false(await fn('afsadgsdcgdcfgefcasfcascfsadf.com'));

 });

 test('invalid domain', async t => {

  try {

  await fn('hi');

  t.fail('Should throw error');

  } catch (err) {

  t.is(err.message, 'Invalid domain');

  }

 });