Add unit tests for controllers

**Problem**
When working with middleware, the error messages could be more descriptive.

**Suggestion**
Improve error handling and add detailed error messages.

**Context**
This would help with debugging and maintenance.

Start by locating the controllers and middleware involved in the issue, then inspect how their current errors are produced and how unit tests are organized. Clarify which error cases need coverage and what information the messages should contain; done means the controller tests cover the middleware failures and the resulting messages are more descriptive.

Written by the indexing model from the issue text.