Assert a message of a given type with a given text is (or is not) on the page. Works in the admin panel and on the storefront. The text may be a part of the message.
Examples
Then I should see the success message "You saved the product."
Then I should see the error message "is not valid."
And I should not see the error message "This is a required field."
Then we should see the success message "You added Joust Duffle Bag to your shopping cart."
Then should see the notice message "Your search returned no results."
Pattern
Then(/^(I |we )*should( not)* see the (success|error|warning|notice) message "([^"]*)"$/, …)
Part of @webship-js/magento-steps (github.com/webship/magento-steps), a step pack for Webship-js 2.0.x.