Assert the website editor is, or is not, open: its panel with the building blocks and the "Save" and "Discard" buttons (#oe_snippets).
Examples
Then I should see the website editor
And I should not see the website editor
Then we should see the website editor
And I should see the editor of the website
Then we should not see the editor of the website
Pattern
Then(/^(I |we )*should( not)* see the (?:website editor|editor of the website)$/, …)
Part of @webship-js/odoo-steps (github.com/webship/odoo-steps), a step pack for Webship-js 2.0.x.