'When a container with no custom environment variables is launched via
``DockerClient.add`` the environment in the resulting ``Unit`` returned
from ``DockerClient.list`` will ignore the default HOME and PATH
environment variables, leaving the ``Unit`` with an Environment of
None.'

def test_empty_environment(self):

    name = random_name(self)
    d = self.start_container(name)
    def started(client):
        deferred_units = client.list()
        def check_units(units):
            unit = [unit for unit in units if (unit.name == name)][0]
            self.assertIsNone(unit.environment)
        deferred_units.addCallback(check_units)
    d.addCallback(started)
    return d
