Once an API ships it doesn't matter how it should behave - how it actually behaves is the important part. Users depend on the existing behaviour and we need a way to ensure that it doesn't change
Behat is a tool that was built to help design software, but it’s actually a great tool for capturing existing behaviour too.
We’ve used these tools to gain confidence to refactor 5+ year old apps by capturing the existing behaviour before making changes. I want to share the secrets we learned with you