Assert the sitemap lists (or does not list) a path of the site. The step reads sitemap-index.xml and the sitemaps it points at, and compares the path of every address, so the site of the build does not matter.
Examples
Then the sitemap should list "/about/"
And the sitemap should list "/posts/first-post/"
But the sitemap should not list "/404/"
Then sitemap should list "/blog/"
And the sitemap should not list "/posts/draft-post/"
Pattern
Then(/^(?:the )?sitemap should( not)* list "([^"]*)?"$/, …)
Part of @webship-js/astro-steps (github.com/webship/astro-steps), a step pack for Webship-js 2.0.x.