Testing with unittest.mock

1. Testing with unittest.mock Ana Hristova
2. ♥ Every tester has the heart of a developer
3. Crowd Investment Platform CONNECTING INVESTORS AND ENTREPRENEURS THROUGH FUNDING ana@fundedbyme.com
5. Sweden
6. unittest.mock Testing library
7. Part of the Python Standard Library as of Python 3.3 unittest.mock
8. For older versions: unittest.mock $ pip install mock
9. unittest.mock helps you create mock objects and make assertions about them
10. How is this helpful?
11. You want to test code that depends on the " date or time
12. You are building a shiny new app … # $ % % % % % & ' ( )
13. Please wait… … while your tests are running *
14. Mock MagicMock patch( )
15. Mock objects Callable
16. Mock objects Create attributes on demand
17. Mock objects Record how you use the attributes
18. Allow you to set return values or limit the available attributes Mock objects
19. Examples
20. >>> class Comment: ... ... def create(self, text, parent=None): ... pass ... comment = Comment()
21. >>> comment.create = Mock(return_value=True) >>> comment.create(text=‘hello') True >>> comment.create. \ ... assert_called_once_with(text=‘hello’) >>> comment.create.called True >>> comment.create.call_args call(text='hello') >>> comment.call_count 1
22. >>> mock = Mock() >>> mock <Mock id='4353021072'> >>> mock.method <Mock name='mock.method' id=‘4352854800'> >>> mock.assetr_called_with(keyword=None)
23. ... AttributeError: Mock object has no attribute 'remove' >>> comment.remove >>> from unittest.mock import create_autospec >>> >>> comment = create_autospec(Comment)
24. side effects
25. >>> comment.create.side_effect = \ ... ConnectionError(“Connection refused”) >>> ... ConnectionError: Connection refused >>> comment.create.mock_calls [call(parent=None, text='Hello')] >>> >>> comment.create(text="Hello", parent=None)
26. magic methods Mocking
27. >>> mock = Mock() >>> mock.__len__ = Mock() >>> mock.__len__.return_value = 42 >>> len(mock) 42 ! !
28. MagicMock with default implementations of magic methods Subclass of Mock
29. >>> mock = MagicMock() >>> int(mock) 1 >>> len(mock) 0 >>> list(mock) [] >>> mock.__int__.called True
30. patch( ) Used to patch objects within the scope of the test
31. #event.py from datetime import date ! class Event(): ! def get_state(self): if self.end_date < date.today(): return "PAST" if self.start_date > date.today(): return "FUTURE" if self.start_date <= date.today() <= self.end_date: return "CURRENT"
32. #test.py from datetime import date ! class EventTests(TestCase): def setUp(self): self.pycon = Event() self.pycon.start_date = date(2014, 5, 20) self.pycon.end_date = date(2014, 5, 21) ! @patch('event.date') def test_event_has_passed(self, mock_date): mock_date.today.return_value = date(2014, 5, 22) assert self.pycon.get_state() == "PAST"
33. @patch('event.date') def test_event_has_passed(self, mock_date): mock_date.today.return_value = date(2014, 5, 22) assert self.pycon.get_state() == "PAST"
34. class UserProfileSaveTests(TestCase): ! def setUp(self): self.profile = UserProfileFactory.build(user=UserFactory()) ! ! @patch("notifications.tasks.subscribe_to_newsletter.delay") def test_subscribe_to_newsletter(self, subscribe_mock): self.profile.newsletter = True self.profile.save() subscribe_mock.assert_called_once_with(self.profile.user)
35. Mock wisely!
36. @anhristova + , anah