Assert the admin panel shows (or does not show) its access denied page ("Sorry, you need permissions to view this content."), which it serves with the status 403 to a user whose role does not allow the page.
Examples
Then I should see the access denied page
Then I should not see the access denied page
And I should see the access denied page
Then we should see the access denied page
And we should not see the access denied page
Pattern
Then(/^(I |we )*should( not)* see the access denied page$/, …)
Part of @webship-js/magento-steps (github.com/webship/magento-steps), a step pack for Webship-js 2.0.x.