How do I hook before the user is created in Behat tests? I have a Behat test where I have a Given user step, and I want to alter some fields (token replacements). Which Behat hook should I use? I know that for Given content, the Behat hook would be @beforeNodeCreate.

Which hook is for users?
Somewhat predictably, which I'm pretty sure is deliberate, it's @beforeUserCreate.

The Drupal Extension Hooks section of the docs has a bit of background in case you need it.