chore: remove redundant code and update merge logic

feat: add support for merging test specs

feat: add logging for merging initial block in YamlFile

feat: add test for redirecting loops

feat: Add unit test for multiple documents in YAML file

fix: Import Mock in test_files.py

fix: handle errors in YamlFile class

test: refactor test file handling and add multiple document support

refactor: Move Opener class outside of TestGenerateFiles

test: add exception handling and improve test structure

docs: Add docstring to test_reraise_exception function

fix: Simplify exception test description

refactor: update import path for start_mark