tests/test_main.py

# -*- coding: utf-8 -*-
import mock

from pytube import YouTube


@mock.patch('pytube.__main__.YouTube')
def test_prefetch_deferred(MockYouTube):
    instance = MockYouTube.return_value
    instance.prefetch_init.return_value = None
    YouTube('https://www.youtube.com/watch?v=9bZkp7q19f0', True)
    assert not instance.prefetch_init.called