Satis is a static Composer repository generator. It can be used to generate a composer repository for development and testing purposes.
This composer repository is used as a “stand in” for https://packages.drupal.org (and possibly Packagist) in testing scenarios.
We will reference the Satis-built composer repository in the repositories section of our test Drupal site’s composer.json.
We install Satis via composer inside ./satis, and you can run it locally using ddev satis.