I was executing a complete run using the "pretty" format when execution ended with:

Fatal error: Call to undefined method Behat\Gherkin\Node\StepNode::getCleanText() in vendor/behat/behat/src/Behat/Behat/Formatter/PrettyFormatter.php on line 746

It seems that only progress and moodle_progress are doing the job. I've tried here pretty, html and junit and all them break badly.

Can be reproduced by executing it against any database and using any browser with params:

--format pretty --name 'Test bulk sorting all categories'

Only tried with 2.7, but I suppose the same will happen with other branches.
Ciao