Is anyone running Nightwatch tests for their Drupal project on Platform.sh, and are you able to provide an example of your setup? Are you integrating with any other 3rd party tools?
I’ve never used (or heard of) Nightwatch before. Full integration tests, though, that need a browser, can only be run post-deploy though. I’d recommend having a deploy hook that triggers whatever command starts Nightwatch only on non-production environments, or possibly only on environments of a certain name.
Details beyond that I couldn’t really speak to, though.