Bug and impact

• source/load_mod_from_source_code.py executed a=b in an empty namespace, so running the newly added example crashed immediately with NameError.

Root cause

• The executed source snippet referenced b without defining it in the supplied namespace.

Fix

• Make the executed snippet self-contained by assigning a literal value to a.
• Add a unittest regression that runs the script with runpy and verifies the printed output and exec namespace value.

Validation

• python3 source/load_mod_from_source_code.py
• python3 -m unittest discover -s tests -v