Assert text existence in Rails functional tests for views

To make tests less brittle, I don't want to use assert_select, eg:

assert_select 'h2.subtitle', shipment.vessel_name

This is too close to implementation, if I change the h2 to h3, my test will fail. I would like something like Capybara#assert_text:

assert_text shipment.vessel_name

that just makes sure the vessel name is display on the page.