If you're getting fatal errors due to missing, required files, there's a good chance that you're running into the issue described here: https://www.previousnext.com.au/blog/using-behat-and-drupaldriver-beware-pathauto
In short, a menu rebuild is being called from outside of the Drupal root, thereby exploding your registry. For me, this was caused by views_content_cache, which calls views_invalidate_cache() and triggers a menu rebuild after certain entity operations. Here's how I got around that.
In your featureContext.php file's __construct() function, add: