unittest Mock

what is it?

flexible mock object intended to replace the use of stubs and test doubles. callable; creates attributes as new mocks when you access them. records how you use them, allowing you to make assertions about what your code has done to them

example

examples from here

from unittest.mock import Mock
mock = Mock()
print(mock) # <Mock id='4561344720'>
 
# mock is not an object that we can use in our code
# we can pass it as an argument:
do_something(mock)
 
# we can also use it to patch an entire library:
json = mock
 
# we can run functions off our mock
json.loads('{"key": "value"}')
 
# and we can assert that our function was invoked:
json.loads.assert_called()

patch

patch() decorators makes it easy to temporarily replace classes in a particular module with a Mock object

python_practice.py

def complex_function():
    # this function can do whatever
    # it currently returns nothing
    print('we did nothing')
 
def function_one():
    # we will get a specific response if our function returns 'banana'
    if complex_function() == 'banana':
        return 'the patch worked'
    return 'failure'

test_python_practice.py

from unittest.mock import patch
from python_practice import function_one
 
@patch('python_practice.complex_function', return_value='banana')
def test_function_one(self):
    # setup
    expected_result = 'the patch worked'
 
    # act
    actual_result = function_one()
 
    #verify
    assert actual_result == expected_result