Assert the page does (or does not) come from the current build. Gatsby inlines the build hash in every page (window.___webpackCompilationHash) and publishes it as page-data/app-data.json; when the two differ, the page was served from an older deploy (a stale cache or a half-uploaded site) and Gatsby reloads it once.
Examples
Then the page should be from the current build
And the page should be from the current build
But the page should not be from the current build
Then page should be from the current build
And the page should be from the current build
Pattern
Then(/^(?:the )?page should( not)* be from the current build$/, …)
Part of @webship-js/gatsby-steps (github.com/webship/gatsby-steps), a step pack for Webship-js 2.0.x.