def test_observe_comment_snapshots(mock_reddit):
    r = mock_reddit.return_value
    patch('praw.')

    yesterday_posts = 10
    today_posts = 20

    # SET UP TEST BY PROPAGATING POSTS AND COMMENTS
    controller, today_post_list, comment_counter = setup_comment_monitoring(r, yesterday_posts, today_posts)
    posts = controller.identify_posts_that_need_snapshotting()
    assert len(posts) == today_posts
    comments = controller.sample_comments(posts)

    ## EXPIRE SOME OF THE COMMENTS
    current_time = datetime.datetime.utcnow()
    expired_time = (current_time - datetime.timedelta(seconds=controller.experiment_settings['intervention_window_seconds'] + 10))
    for i in range(0, math.floor(len(comments)/2)):
        comments[i].created_utc = expired_time
    db_session.commit()

    ## LOAD COMMENT FIXTURES
    comment_fixtures = []
    filename = "{script_dir}/fixture_data/comments_0.json".format(script_dir=TEST_DIR)
    f = open(filename, "r")
    comment_fixtures = json.loads(f.read())
    f.close()