Assert the structure board has (or does not have) a placeholder, by the name the page template gives it. The step opens the board when needed.
Examples
Then I should see the "Page Content" placeholder
Then I should not see the "Sidebar" placeholder
And we should see the "Page Content" placeholder
Then should see the "Footer" placeholder
But we should not see the "Header" placeholder
Pattern
Then(/^(I |we )*should( not)* see the "([^"]*)" placeholder$/, …)
Part of @webship-js/django-cms-steps (github.com/webship/django-cms-steps), a step pack for Webship-js 2.0.x.