Python | Unit Test Objects Patching | Set-2 Last Updated : 12 Jun, 2019 Comments Improve Suggest changes Like Article Like Report MagicMock instances that are normally used as replacement values are meant to mimic callables and instances. They record information about usage and allow to make assertions as shown in the code given below - Code #6: Python3 1== from unittest.mock import MagicMock m = MagicMock(return_value = 10) print(m(1, 2, debug = True), "\n") m.assert_called_with(1, 2, debug = True) m.assert_called_with(1, 2) Output : 10 Traceback (most recent call last): File "", line 1, in File ".../unittest/mock.py", line 726, in assert_called_with raise AssertionError(msg) AssertionError: Expected call: mock(1, 2) Actual call: mock(1, 2, debug=True) Code #7 : Replacing the value by supplying it as a second argument to patch() Python3 1== print("x : ", x) with patch('__main__.x', 'patched_value'): print(x) patched_value print("x : ", x) Output : x : 42 x : 42 MagicMock instances that are normally used as replacement values are meant to mimic callables and instances. They record information about usage and can make assertions. Python3 1== from unittest.mock import MagicMock m = MagicMock(return_value = 10) print(m(1, 2, debug = True), "\n") m.assert_called_with(1, 2, debug = True) m.assert_called_with(1, 2) Output : 10 Traceback (most recent call last): File "", line 1, in File ".../unittest/mock.py", line 726, in assert_called_with raise AssertionError(msg) AssertionError: Expected call: mock(1, 2) Actual call: mock(1, 2, debug=True) Code #8 : Working on the example Python3 1== m.upper.return_value = 'HELLO' print (m.upper('hello')) assert m.upper.called m.split.return_value = ['hello', 'world'] print (m.split('hello world')) m.split.assert_called_with('hello world') print (m['blah']) print (m.__getitem__.called) Output : 'HELLO' ['hello', 'world'] <MagicMock name='mock.__getitem__()' id='4314412048'> True Typically, these kinds of operations are carried out in a unit test. It is explained with an example taking a function in the code given below - Code #9 : Python3 1== from urllib.request import urlopen import csv def dowprices(): u = urlopen('http://finance.yahoo.com/d/quotes.csv?s =@^DJI&f = sl1') lines = (line.decode('utf-8') for line in u) rows = (row for row in csv.reader(lines) if len(row) == 2) prices = { name:float(price) for name, price in rows } return prices Normally, this function uses urlopen() to go fetch data off the Web and parse it. To unit test it, a more predictable dataset can be used. Comment More infoAdvertise with us Next Article Python | Unit Test Objects Patching | Set-2 M manikachandna97 Follow Improve Article Tags : Python Python-ctype Practice Tags : python Similar Reads 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 use 2 min read Object oriented testing in Python Prerequisite: Object-Oriented Testing Automated Object-Oriented Testing can be performed in Python using Pytest testing tool. In this article, we perform object-oriented testing by executing test cases for classes. 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