When I scroll

Assert every <img> on the page has an alt attribute.

Empty alt="" is allowed (decorative images per WCAG); role="presentation"
is also allowed. Only a missing alt attribute fails. Iterates every <img>
in the document, including those nested in shadow-light DOM that the page
has rendered, so it works on infinite-scroll lists and image galleries too.

Step pattern

Then every image should have an alt attribute

Examples

Then every image should have an alt attribute

And every image should have an alt attribute

Given I am on "/photos"
Then every image should have an alt attribute

When I scroll to the bottom
Then every image should have an alt attribute

When I follow "Gallery"
Then every image should have an alt attribute