Python Mocking with unitest.mock

External

• https://docs.python.org/3/library/unittest.mock.html#module-unittest.mock

Internal

• unittest Module

Mocking

To mock a class and a method of that class:

from unittest.mock import Mock


class SomeClass:
    def __init__(self, state):
        self.state = state

    def some_method(self):
        return self.state


sc = SomeClass('A')
assert 'A' == sc.some_method()

sc_mock = Mock(SomeClass)
sc_mock.some_method = Mock(return_value='blah')

assert 'blah' == sc_mock.some_method()

How to simulate different return values for a mocked function depending on an argument value?

Mocking a Property

https://docs.python.org/3/library/unittest.mock.html#unittest.mock.PropertyMock

from unittest.mock import patch, PropertyMock

class A:
    @property
    def property_a(self):
        return "pa"

with patch('__main__.A.property_a', new_callable=PropertyMock) as mock_property:
    mock_property.return_value = 'mocked pa'
    a = A()
    assert a.property_a == 'mocked pa'

Mocking a Method

from unittest.mock import patch

class A:
    def method_a(self):
        return "ma"

with patch.object(A, 'method_a', return_value='mocked ma') as mock_method:
    a = A()
    assert a.method_a() == 'mocked ma'