Contract tests of the public API were added to Balrog in https://github.com/mozilla/balrog/pull/210. The initial intention is to run these on Cloudops QA infrastructure as part of the deployment process, but it would be good to run them as part of CI as well. The big difference with running them in CI is that they'll need to query using Flask's TestClient instead of a real web server. This probably also means that they should import a production database dump, so that queries don't always return empty update responses. It's probably easiest to add a new Task to do this rather than trying to run it as part of the existing backend tests.