The bug was not exposed by the original test, since it was mixing two (related) aspects:
* An invalid Id (a badly formed mongodb identifier)
* An non-existent Id (an identifier with no corresponding document in the database)
Modifications:
- Fixed the message property in the article controller (the error message follows the wording of the error message in "users.password.server.controller.js", in case of username not found)
- Added a new test to check modifications and avoid regressions
