Add unit tests for middleware

**Problem**
When working with store, 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 middleware and store code mentioned in the issue, then find the existing unit-test structure for those components. Compare current error handling with the requested more descriptive messages; done means the relevant middleware behavior has unit-test coverage and the resulting errors provide useful debugging detail.

Written by the indexing model from the issue text.