.validate_single_guid: Validate a single GUID test ID
Description
Internal helper to validate that exactly one non-empty, non-NA,
string-based GUID has been supplied.
Usage
.validate_single_guid(..., arg_name = "`test_id`")
Value
A single validated test ID string.
Internal function (not designed to be used directly by end users)
Arguments
- ...
One or more values for the test ID.
- arg_name
Optional string for the argument name to use in error messages.