page_cache not working in test_missing_pre_or_code_query

What happened:

Fork and clone the repository to local. I ran the test with python3 -m test_howdoi. I get the following result.

Traceback (most recent call last):
  File "/Users/XXX/Projects/howdoi/test_howdoi.py", line 270, in test_missing_pre_or_code_query
    self.assertIn('XML elements present in a XML', output)
AssertionError: 'XML elements present in a XML' not found in '<people>\n    <student>\n        <name>John</name>\n    </student>\n</people>\n'

What you expected to happen:

If the page_cache was working, the test should pass. However, for some reason, it is not using page_cache and fetching the latest answer from stackoverflow, which has different order compared to cached_html, resulting in test failure.