Python Unit Testing

---

Unit Testing

https://chase-seibert.github.io/blog/2015/06/25/python-mocking-cookbook.html
https://santexgroup.com/wp-content/uploads/2014/10/mock_python.html#slide17

@patch function

• patching the function of aiohttp.ClientSession.request,

@patch(f'aiohttp.ClientSession.request')
def test_dispatch_send_should_call_session_request(
    self, mock_client_session_request,
):

• patching internal function of compute_wakeup_delay of RequestProgressTracker

MODULE = 'project.util.reqtracker.RequestProgressTracker'

@patch(f'{MODULE}._compute_wakeup_delay', return_value=0)
def test_ack_request_should_remove_request_attribute(
        self, mock_compute_wakeup_delay
):

• patching object attribute

>>> @patch('package.module.ClassName.attribute', sentinel.attribute)
... def test():
...     from package.module import ClassName
...     assert ClassName.attribute == sentinel.attribute
...
>>> test()

>>> class MyTest(unittest.TestCase):
...     @patch.object(SomeClass, 'attribute', sentinel.attribute)
...     def test_something(self):
...         self.assertEqual(SomeClass.attribute, sentinel.attribute)
...
>>> original = SomeClass.attribute
>>> MyTest('test_something').test_something()
>>> assert SomeClass.attribute == original

>>> class MyTest(unittest.TestCase):
...     @patch.object(SomeClass, 'static_method')
...     def test_something(self, mock_method):
...         SomeClass.static_method()
...         mock_method.assert_called_with()
...
>>> MyTest('test_something').test_something()

Mock / MagicMock

• Patch return value of a function.

func1 = MagicMock(return=('POST', {} , '/add'}

• Patch return value of object attribute.

object.age = PropertyMock(return_value=34)

side_effect

A useful attribute is side_effect. If you set this to an exception class or instance then the exception will be raised when the mock is called.

>>> mock = Mock(side_effect=Exception('Boom!'))
>>> mock()
Traceback (most recent call last):
  ...
Exception: Boom!

Example

@patch('time.time', MagicMock(return_value=1530667543.3568835))

#!/usr/bin/env python
# -*- coding: utf-8 -*-

from mymodule import rm

import mock
import unittest

class RmTestCase(unittest.TestCase):
    
    @mock.patch('mymodule.os.path')
    @mock.patch('mymodule.os')
    def test_rm(self, mock_os, mock_path):
        # set up the mock
        mock_path.isfile.return_value = False
        
        rm("any path")
        
        # test that the remove call was NOT called.
        self.assertFalse(mock_os.remove.called, "Failed to not remove the file if not present.")
        
        # make the file 'exist'
        mock_path.isfile.return_value = True
        
        rm("any path")
        
        mock_os.remove.assert_called_with("any path")

assert_called_once_with(*args, **kwargs)

>>> mock = Mock(return_value=None)
>>> mock('foo', bar='baz')
>>> mock.assert_called_once_with('foo', bar='baz')
>>> mock('other', bar='values')
>>> mock.assert_called_once_with('other', bar='values')
Traceback (most recent call last):
  ...
AssertionError: Expected 'mock' to be called once. Called 2 times.

Assert that the mock was called exactly once and that that call was with the specified arguments.