'``FigConfiguration._parse_app_environment`` returns a ``frozenset``
of environment variable name/value pairs given a valid configuration.'

def test_valid_fig_config_environment(self):

    config = {u'postgres': {u'image': u'sample/postgres', u'environment': {u'PG_SCHEMA_NAME': u'example_database', u'PG_PGUSER_PASSWORD': u'clusterhq'}}}
    parser = FigConfiguration(config)
    expected_result = frozenset(config[u'postgres'][u'environment'].items())
    environment = parser._parse_app_environment(u'postgres', config[u'postgres'][u'environment'])
    self.assertEqual(expected_result, environment)
