Pass / fail sync act

test-sync-act.js

it('should render with the correct text without act', () => {
  ReactDOM.render(<App/>, el);
  expect(el.innerHTML).toContain('unloaded val');
});

it('should render with the correct text with act', () => {
  act(() => {
    ReactDOM.render(<App/>, el);
  });
  expect(el.innerHTML).toContain('sync val');
});