Add unit tests for helpers

**Problem**
When working with config, 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 config helpers and the existing unit-test setup first, since the issue does not name specific files or entry points. Define the expected detailed error messages for config failures, add unit tests covering them, and consider the work done when those tests verify the improved debugging context.

Written by the indexing model from the issue text.