Class with dependencies

class_dependencies.py

from unittest import TestCase
from mock import patch
import external_module

class SomeHandler(object):
    def authenticate_login(self):
        external_module.authenticate()
        external_module.login()


class TestSomeHandler(TestCase):
    @patch('external_module.authenticate')
    def test_authenticate_login_should_call_authenticate(self, authenticate_mock):
        SomeHandler()
        authenticate_mock.assert_called()

constructor_injection.py

import external_module

class SomeHandler(object):
    def __init__(self, _auth=None, _login=None):
        self.authenticate = _auth or external_module.authenticate
        self.login = _login or external_module.login

    def authenticate_login(self):
        self.authenticate()
        self.login()