Add unit tests for middleware

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

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

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

Locate the middleware implementation and the project's unit-test entry point; first inspect how current API errors are handled. Add tests covering the requested descriptive error behavior, then run the relevant middleware test command and confirm the error messages provide more debugging detail.

Written by the indexing model from the issue text.