Assert the elements that persist across navigation (transition:persist) were kept: after the last client-side navigation they are the same elements that were on the page before, not new copies, so their state (a playing video, an island's counter) is kept.
Examples
Then the persistent elements should have been kept
And the persistent elements should have been kept
But the persistent elements should not have been kept
Then persistent elements should have been kept
And the persistent elements should have been kept
Pattern
Then(/^(?:the )?persistent elements should( not)* have been kept$/, …)
Part of @webship-js/astro-steps (github.com/webship/astro-steps), a step pack for Webship-js 2.0.x.