Testing based on roles and permissions based website

What would be the best approach or the best tool for testing a drupal based website that deals mainly with roles and permissions? Just an insight. I am currently thinking about behat being the best tool in order to do the testing on such a website. but any other suggestions? any other insights on the topic. its a website that builds another website or an intranet service. different types of roles are assigned different types of permissions in order to perform the build. behat still the best approach for automated testing or any other tool would help. behat is one of the best toold for drupal based websites, my question is more specific only because it involves a lot of users haveing various different roles and permissions. thank you world :)