Testing with unittest.mock

Transcript

1. Testing
   with
   unittest.mock
   Ana Hristova
   

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2. ♥
   Every tester has
   the heart of a
   developer
   

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3. Crowd Investment Platform
   CONNECTING INVESTORS AND ENTREPRENEURS
   THROUGH FUNDING
   ana@fundedbyme.com
   

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5. Sweden
   

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6. unittest.mock
   Testing library
   

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7. Part of the Python Standard
   Library as of Python 3.3
   unittest.mock
   

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8. For older versions:
   unittest.mock
   $ pip install mock
   

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9. unittest.mock helps you
   create mock objects
   and make assertions
   about them
   

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10. How is this helpful?
    

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11. You want to test code that
    depends on the
    "
    date or time
    

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12. You are
    building a
    shiny new
    app …
    #
    $
    % %
    % %
    %
    &
    ' (
    )
    

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13. Please wait…
    … while your tests are running
    *
    

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14. Mock
    MagicMock
    patch( )
    

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15. Mock objects
    Callable
    

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16. Mock objects
    Create attributes on demand
    

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17. Mock objects
    Record how you use the
    attributes
    

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18. Allow you to set return values or
    limit the available attributes
    Mock objects
    

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19. Examples
    

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20. >>> class Comment:
    ...
    ... def create(self, text, parent=None):
    ... pass
    ...
    comment = Comment()
    

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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
    

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22. >>> mock = Mock()
    >>> mock
    
    >>> mock.method
    
    >>> mock.assetr_called_with(keyword=None)
    

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23. ...
    AttributeError: Mock object has no attribute
    'remove'
    >>> comment.remove
    >>> from unittest.mock import create_autospec
    >>>
    >>> comment = create_autospec(Comment)
    

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24. side effects
    

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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)
    

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26. magic methods
    Mocking
    

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27. >>> mock = Mock()
    >>> mock.__len__ = Mock()
    >>> mock.__len__.return_value = 42
    >>> len(mock)
    42
    !
    !
    

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28. MagicMock
    with default implementations
    of magic methods
    Subclass of Mock
    

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29. >>> mock = MagicMock()
    >>> int(mock)
    1
    >>> len(mock)
    0
    >>> list(mock)
    []
    >>> mock.__int__.called
    True
    

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30. patch( )
    Used to patch objects
    within the scope of the test
    

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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"
    

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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"
    

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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"
    

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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)
    

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35. Mock wisely!
    

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36. @anhristova
    +
    , anah
    

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