Assert how many products the list found, over all its pages (the "Items 1-12 of 15" or "6 Items" of the toolbar).
Examples
Then the product list should have 15 products
Then the product list should have 6 products
And the product list should have 1 product
Then the product list should have 30 products
Then the product list should have 9 products
Pattern
Then(/^the product list should have (\d+) products?$/, …)
Part of @webship-js/magento-steps (github.com/webship/magento-steps), a step pack for Webship-js 2.0.x.