Testing with unittest.mock

Transcript

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

4. None

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