'Config: add_extra_torznab'

@TestArgs(([], [''], ['']), ([], 'ABCDEF', ['A', 'B', 'C', 'D', 'E', 'F']), ([1, 2, [False, True]], ['3', [0, 0]], [1, 2, [False, True], '3', [0, 0]]))
def test_add_extra_torznab(self, initial, added, expected):

    path = '/tmp/notexist'
    self.config_mock['Torznab'] = {'extra_torznabs': initial}
    c = headphones.config.Config(path)
    c.add_extra_torznab(added)
    act = self.config_mock['Torznab']['extra_torznabs']
    self.assertEqual(act, expected)
