'Very simple test just to make sure update_available_resource is
called as expected.'

@mock.patch('nova.context.get_admin_context')
def test_pre_start_hook(self, get_admin_context):

    with mock.patch.object(self.compute, 'update_available_resource') as update_res:
        self.compute.pre_start_hook()
    update_res.assert_called_once_with(get_admin_context.return_value, startup=True)
