Fixed testWordExtraction not to depend on installed modules

Instead, can we do something like:
```py
words = [
    'MUSIC', 'SPOTIFY'
]

mock_module = Mock()
mock_module.WORDS = [
    'MOCK'
]
words.extend(mock_module.WORDS)
```
This avoids inconsistencies between `WORDS` and `mock_module.WORDS`.