'test_delete
CouchBackend.delete should return and take two params
db conn to pycouchdb is mocked.
TODO Should test on key not exists'

def test_delete(self):

    x = CouchBackend(app=self.app)
    x._connection = Mock()
    mocked_delete = x._connection.delete = Mock()
    mocked_delete.return_value = None
    assert (x.delete(u'1f3fab') is None)
    x._connection.delete.assert_called_once_with(u'1f3fab')
