Add unit tests for config

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

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

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

No files, tests, or entry points are named. Start by locating the config and component error-handling code, then identify how errors are currently tested; done means coverage for the relevant cases and more descriptive error messages.

Written by the indexing model from the issue text.