Update test TestFile.test_open_returns_file_object in tests/unit/file/test_file.py
Update test TestFile.test_open_returns_file_object in tests/unit/file/test_file.py

Specifically, adds sub-tests to verify that a File object, when its .open() method is used as a context manager,
returns a Python file object.

SizzlingVortex/classyfd