Assert the current page was (or was not) built by Gatsby, by its generator meta tag. The markup phrasing ("the Gatsby generator meta tag") and the site phrasing ("generated by Gatsby") are one step.
Examples
Then the page should be generated by Gatsby
Then we should see the Gatsby generator meta tag
And the page should not be generated by Gatsby
Then should see the Gatsby generator meta tag
Then page should be generated by Gatsby
Pattern
Then(/^(?:(?:I |we )*should( not)* see the Gatsby generator meta tag|(?:the )?page should( not)* be generated by Gatsby)$/, …)
Part of @webship-js/gatsby-steps (github.com/webship/gatsby-steps), a step pack for Webship-js 2.0.x.