check visible text isn't show up in DOM while Cucumber scenarios run

I'm using Cucumber and Watir in my web automation project (written in Ruby). I've a set of feature files with scenarios that I am constantly running. I've received a task to add an additional global check that makes sure that a set of strings does not show up on any of the DOM of any of the pages in any of the scenarios that I run.

For example, I've a scenario called 'Login to environment'. While running through that scenario and the normal flow for logging into the environment, I need something that also checks that some string bla doesn't show up in any of the HTML DOM. Also, I need this to happen for every other scenario that I have.

What is the correct way to implement such functionality in Cucumber/Watir/Ruby?