We need a view on the content.
>>> request = self.app.REQUEST
>>> from zope.publisher.browser import BrowserView
>>> view = BrowserView(self.portal, request)
>>> from plone.app.layout.viewlets.interfaces import IPortalFooter
>>> from Products.Five.viewlet.manager import ViewletManager
>>> Footer = ViewletManager('left', IPortalFooter)
Now we can instantiate the manager.
>>> manager = Footer(self.portal, request, view)
Set analytics (webstats_js) code through the controlpanel
>>> props = self.portal.portal_properties.site_properties
>>> props.webstats_js = u""
>>> manager.update()
>>> text = manager.render()
>>> props.webstats_js in text
True
Now enter some non-ascii text
>>> props.webstats_js = u""
>>> manager.update()
>>> text = manager.render()
>>> props.webstats_js in text
True