Add unit tests for data

**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.

Start by locating the component error-handling paths and the existing unit-test setup. Review how current errors are reported, then define the missing descriptive messages and tests; done means the relevant component failures produce clearer errors and the unit tests pass.

Written by the indexing model from the issue text.