I just suggested to rewrite it so:
```python
def is_video_rendered(self, mode):
    """
    Check that if video is rendered in `mode`.
    :param mode: Video mode, `html5` or `youtube`
    """
    modes = {
        'html5': 'video',
        'youtube': 'iframe'
    }

    html_tag = modes[mode]
    css = '.video {0}'.format(html_tag)

    return EmptyPromise(lambda: self.q(css=css).present,
                 'Video Rendering Failed in {0} mode.'.format(mode)).fulfill()
```
For tests for mobile devices, `self.q(css='.speed_link').present` will return False. Native controls are used on mobile devices, so `.speed_link` will not be present on the page.