Python | Unit Test Objects Patching | Set-1

The problem is writing unit tests and need to apply patches to selected objects in order to make assertions about how they were used in the test (e.g., assertions about being called with certain parameters, access to selected attributes, etc.).

To do so, the unittest.mock.patch() function can be used to help with this problem. It’s a little unusual, but patch() can be used as a decorator, a context manager, or stand-alone.

Code #1: Using unittest.mock.patch as a decorator



filter_none

edit
close

play_arrow

link
brightness_4
code

from unittest.mock import patch
import example
@patch('example.func')
  
def test1(x, mock_func):
    # Uses patched example.func
    example.func(x) 
    mock_func.assert_called_with(x)

chevron_right


 
Code #2: Using unittest.mock.patch as a decorator

filter_none

edit
close

play_arrow

link
brightness_4
code

with patch('example.func') as mock_func:
    example.func(x) 
    mock_func.assert_called_with(x)

chevron_right


 
Code #3: Using unittest.mock.patch to patch things manually.

filter_none

edit
close

play_arrow

link
brightness_4
code

p = patch('example.func')
mock_func = p.start()
example.func(x)
mock_func.assert_called_with(x)
p.stop()

chevron_right


 
Code #4: Stacking decorators and context managers to patch multiple objects

filter_none

edit
close

play_arrow

link
brightness_4
code

@patch('example.func1')
@patch('example.func2')
@patch('example.func3')
  
def test1(mock1, mock2, mock3):
    ...
def test2():
    with patch('example.patch1') as mock1, \
    patch('example.patch2') as mock2, \
    patch('example.patch3') as mock3:
    ...

chevron_right


patch() works by taking an existing object with the fully qualified name that you provide and replacing it with a new value. The original value is then restored after the completion of the decorated function or context manager. By default, values are replaced with MagicMock instances.
 
Code #5 : Example

filter_none

edit
close

play_arrow

link
brightness_4
code

x = 42
with patch('__main__.x'):
    print(x)
  
print (x)

chevron_right


Output :

<MagicMock name='x' id='4314230032'>
42


My Personal Notes arrow_drop_up

Check out this Author's contributed articles.

If you like GeeksforGeeks and would like to contribute, you can also write an article using contribute.geeksforgeeks.org or mail your article to contribute@geeksforgeeks.org. See your article appearing on the GeeksforGeeks main page and help other Geeks.

Please Improve this article if you find anything incorrect by clicking on the "Improve Article" button below.




Article Tags :

Be the First to upvote.


Please write to us at contribute@geeksforgeeks.org to report any issue with the above content.