(Medium) - Decouple Side-Effects

AllowsToFilterTheListOfPosts.js

QUnit.test('Allows to filter the list of posts', (assert) => {
  const inMemoryDataSource = {
    findPostsTitle: () => Promise.resolve(['How to bake a cake', 'How to drive a car', 'A guide to fly']),
  };
  const ignoreOutHowTos = (postTitle) => postTitle.indexOf('How to') !== -1;

  const listOfPostTitles = ListOfPostTitles();
  listOfPostTitles.setDataSource(inMemoryDataSource);

  return listOfPostTitles.toHtml(ignoreOutHowTos).then((list) => {
    assert.strictEqual(list, '<ul><li>A guide to fly</li></ul>');
  });
});