I think this is overselling itself a little. It seems genuinely useful to be able to do more expansive integration tests of components, and combinations of components, especially running in real browsers. But that’s only really an incremental gain over component unit tests with mocks. In the case where you own a very complex SPA with multiple back end dependencies you don’t control, then yeah, maybe this is all you need. But I don’t see how this can replace real end to end functional tests in most apps.