Assert the permalink structure selected on Settings > Permalinks, by its name.
Examples
Then the permalink structure should be "Post name"
And the permalink structure should be "Day and name"
Then the permalink structure should not be "Plain"
And the permalink structure should not be "Numeric"
Then the permalink structure should be "Month and name"
Pattern
Then(/^the permalink structure should( not)* be "([^"]*)"$/, …)
Part of @webship-js/wordpress-steps (github.com/webship/wordpress-steps), a step pack for Webship-js 2.0.x.