Add unit tests for helpers

**Problem**
When working with data, 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 does not name a helper file, test file, or entry point. First locate the helper implementations and existing unit-test setup, then identify the data-related failures and define detailed error-message expectations; done means focused tests cover the relevant helpers and pass with the improved messages.

Written by the indexing model from the issue text.