Add unit tests for hooks

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

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

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

The issue identifies hooks, models, and error handling but names no files or existing tests. Start by locating the hook implementation and unit-test entry points in the Shell repository, then clarify which error messages and hook behaviors are in scope. Done means agreed cases have tests and the relevant errors are more descriptive.

Written by the indexing model from the issue text.