If you don't have a test entry point, it's not obvious that you need one or you need to fix your index.js

[jalada]

Related Pivotal Tracker ticket: https://www.pivotaltracker.com/story/show/179970095

If you don't have an index.test.js, cavy-cli silently assumes you've altered your index.js already to wrap your app in a <Tester> component. This feels like throwback behaviour to v. early Cavy days and probably something we should fix.

We should warn the user if cavy-cli doesn't find a test entry file, otherwise they might feel like its broken.