This is a test of presence.

To test this service we will start up a mock dbus library:

    >>> from sugar.testing import mockdbus
    >>> import dbus
    >>> pres_service = mockdbus.MockService(
    ...     'org.laptop.Presence', '/org/laptop/Presence', name='pres')
    >>> pres_service.install()
    >>> pres_interface = dbus.Interface(pres_service, 'org.laptop.Presence')

Then we import the library (second, to make sure it connects to our
mocked system, though the lazy instantiation in get_instance() should
handle it):

    >>> from sugar.presence import PresenceService
    >>> ps = PresenceService.get_instance()
    >>> pres_interface.make_response('getServices', [])
    >>> ps.get_services()
    Called pres.org.laptop.Presence:getServices()
    []
    >>> pres_interface.make_response('getBuddies', [])
    >>> ps.get_buddies()
    Called pres.org.laptop.Presence:getBuddies()
    []