Bug and impact

Running source/load_mod_from_source_code.py crashed immediately with NameError: name 'b' is not defined, making the newly added source-loading example unusable.

Root cause

The executed snippet was a=b, but the script passed an empty namespace to exec, so b was never defined.

Fix and validation

• Made the executed snippet self-contained by assigning the literal value to a.
• Added a regression test that runs the script with the current Python interpreter and verifies clean output.
• Validated with:
  • python3 source/load_mod_from_source_code.py
  • python3 -m unittest discover
  • python3 source/unittest_to_io.py