Whilst reviewing MDL-82424 I've discovered the inner workings of this tool and how its essentialyl duplicating parts of the inner workings of Behat, but doing so incorrectly.

Essentially this approach is not ideal and we should replace the steprunner and the runner with a custom Behat test runner.

If we were to do this then we would be correclty supporting all of the supported Turnip and Regexp pattern types of Behat, as well as the (not-so-new) Behat PHP Attributes for Given, When, Then, etc.