The Perils of Parallel Testing in Ruby on Rails
Have you ever heard someone complain about their tests being too fast? Me neither. Fast tests mean fast feedback. Whether you run them locally or in a continuous integration pipeline, the earlier your tests finish, the earlier you can react to failures and improve your code. Besides the productivity gains, it is well known that slow tests make developers grumpy. Nobody likes their developers grumpy. With all that said, creating a lightning-fast test suite isn't always as easy as you'd hope.