Python Mocking with unitest.mock
External
Internal
Overview
The unittest.mock
library allows replacing parts of the system under test with mock objects and make assertion about how they are accessed and used.
Mock
By default, a Mock
accept any invocations into it.
MagicMock
Difference between Mock
and MagicMock
.
patch() and @patch
Sentinel
TODEPLETE
https://realpython.com/python-mock-library/
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
Tested to work:
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'
Mocking a Function of a Module
Use patch()
as a context manager. Inside the with
statement, the `target` (the first argument of patch()
) is patched with a `new` object. When the with
statement exits, the patch is undone. If the 'new' is committed, the target is replaced with a MagicMock, and the created mock is returned by the context manager.
Asserting Method Invocation
mock.assert_called_once_with(
"some concrete arg 1",
unittest.mock.ANY)
TO further document: https://docs.python.org/3/library/unittest.mock.html#unittest.mock.ANY