Assert the page links a valid web app manifest (gatsby-plugin-manifest): it is JSON, it has a name and a start URL, and every icon it lists is served as an image.
Examples
Then the web app manifest should be valid
And the web app manifest should be valid
Then web app manifest should be valid
And the manifest should be valid
Then we should see a valid web app manifest
Pattern
Then(/^(?:(?:I |we )*should see a valid web app manifest|(?:the )?(?:web app )?manifest should be valid)$/, …)
Part of @webship-js/gatsby-steps (github.com/webship/gatsby-steps), a step pack for Webship-js 2.0.x.