Open the preview of the post or page from the editor and wait for the preview frame.
Examples
When I preview the post
When I preview the page
When we preview the post
And I preview the post
And we preview the page
Pattern
When(/^(?:I |we )?preview the (?:post|page)$/, …)
Part of @webship-js/ghost-steps (github.com/webship/ghost-steps), a step pack for Webship-js 2.0.x.