Note: All new APIs are unit tested The only changes to current behaviour are to switch to use of the new API for settings/getting preferences and these are currently behat tested in a number of locations Admin UI test Log in as admin Navigate to Site admin -> Development -> Moodle REST API UI (SwaggerUI) Confirm the page loads without error Confirm that the URL shown underneath "Moodle LMS" ends with: /r.php/api/rest/v2/openapi.json *Confirm that you are shown a page with a number of options (core, user, GET/POST, etc). Smoke test This is best performed by an experienced develoepr Things to try: Use the Swagger UI to play with the various defined endpoints. Do things like: fetch all preferences fetch a single preference Set a single preference ( drawer-open-block is a good one) Set a single preference to an invalid value Set a preference which does not exist Get a preference which does not exist Set/Get multiple preferences Fetch a single template (e.g. core/modal ) Fetch a template with dependencies (e.g. core/notification ) Incldue/exclude comments when fetching templates Install a different site language and fetch the template for a different language More things to try Edit config.php and set $CFG->debugdisplay = false; Tail your php error log Edit an existing service and modify the attributes in such a way that they break, for example: Edit lib/classes/route/api/templates.php: find the pathtypes , then make a typo in the class name for the path_themename Check the Swagger UI and confirm that the page loads without the relevant service The error log should be filled with useful information on the problem Undo that, and copy one of the query parameters into the path types Check the Swagger UI and confirm that the page loads without the relevant service The error log should be filled with useful information on the problem Undo that and insert parser exception in (e.g. replace class templates with cla ss templates ) Check the Swagger UI and confirm that the page loads without the relevant service The error log should be filled with useful information on the problem Repeat the above with debugdisplay set to true - you'll have to look directly at the openapi.json URI instead of the Swagger UI page Play around with $CFG->debug_developer_use_pretty_exceptions = false; in both true/false settings too