Last week Frederik asked about DPS on Drupal Commerce (Commerce DPS is a Drupal payment module I maintain, but which I hadn't had a chance to road test the Drupal 8 version of). I figured I should get familiar!
I ran up a Commerce Demo site with DPS payments and threw a Behat test on it locally. Then made that all execute in CI.
Cos I'm thinking about Treasury re-usable process I used my drupal-builder tool to kick things off. This is a tool which implements the "New Drupal Site" process, but is IMO tidier and more reproducible on account of demonstrating ideas from Drupal new project proposal.
I also implemented inserting creds into Drupal configuration from Gitlab variables to CI runs, because I didn't want to expose them on a public project.
I included some example things such as taking screenshots (see CI/CD => latest pipeline => test behat => files) and checking out via configured DPS gateway.
Next step: fix the Commerce DPS tests :)