def METHOD_NAME(self):
    # Mock response for listing the snapshots
    responses.add(responses.GET, self.snapshot_url + '/_all', json=SNAPSHOTS_LIST, status=200)
    # Set up a mock responses for deleting the snapshots
    for s in SNAPSHOTS_LIST['snapshots']:
        responses.add(responses.DELETE, self.snapshot_url + '/' + s['snapshot'], json={"acknowledged": True}, status=200)
    # Set the time to the day of the latest backup, and request a prune
    latest_fixture_date = datetime.utcfromtimestamp(SNAPSHOTS_LIST['snapshots'][-1]['start_time_in_millis'] / 1000)
    with freeze_time(latest_fixture_date):
        # Ensure the client correctly deletes snapshots up to our specified threshold
        client = snapshot.ESSnapshotsClient(self.es_conn, self.snap_repo)
        client.prune_snapshots(ttl_days=4)
        assert client.snapshots == []                     # This just checks we reached the end of the deletion code
    # We can't really test anything more here - we don't have a remote system that will actually respond to deletes,
    # so if I mock the next list_snapshots call I'd just be testing how good the fixtures are.