Set Moodle DEBUG >= NORMAL Get the REST demo client: https://github.com/moodlehq/moodle-local_wstemplate Test both JSON and XML format (you can change it in the demo client) Tests to execute for both format: one call that is valid (run the client once, it creates two user. If the test users already exist, delete them) one call that return an exception (any other run of the client when the users are already created) one call that is valid with a missing value in the return value (Delete all previously created test users. Hack the create users external function to return an incomplete value. The REST server should return an error) one call that is valid with a unexpected value in the return value (Delete all previously created test users. Hack the create users external function to return more values. The REST server should not return any error)