Assert a menu has (or does not have) a link, read from its list of links in the administration (enabled or not).
Examples
Then the "Primary navigation" menu should have the link "Home"
Then the "Primary navigation" menu should have the link "About"
And the "Primary navigation" menu should not have the link "Notes"
Then the "Account menu" menu should have the link "Log out"
And the "Primary navigation" menu should not have the link "Hive tour"
Pattern
Then(/^the "([^"]*)" menu should( not)* have the link "([^"]*)"$/, …)
Part of @webship-js/backdrop-cms-steps (github.com/webship/backdrop-cms-steps), a step pack for Webship-js 2.0.x.