Behat has always suggested using PHPUnit as a possible assertion library.

Unfortunately as reported by @loru88 in #1617 and confirmed in sebastianbergmann/phpunit#6175 this does not work as of PHPUnit 11.3.0 and will not be reinstated. 😢

At very least we need to update the Behat docs to remove the PHPUnit recommendation.

We might also want to consider recommending a migration path for users with existing projects (I already know that this will have a big impact on my company's projects when we bump up from PHPUnit 10)...

The other impact is that Behat currently formats PHPUnit assertions differently from generic exceptions when reporting failures - we should consider whether we want to extend that treatment to any other assertion libraries.