[英]How to properly mock private members of a class
我正在嘗試為依賴於另一個私有方法的方法編寫一些單元測試。 -如下例所示:
def is_member_of(self, group_name):
members = self.__get_group_members(group_name)
我想模擬的私有方法是__get_group_members
; 我還想模擬私有屬性__user_id
因為它將在is_member_of
函數中使用(在上面的示例中未顯示)。
到目前為止,我有:
import unittest
from unittest import mock
class Test(unittest.TestCase):
group_data = []
user_id = 'test_user_id'
def mock_dependencies(self, x):
x.__user_id = mock.PropertyMock(return_value=self.user_id)
x.__get_group_members = mock.MagicMock(return_value=self.group_data)
def first_test(self):
x = A(('name', 'group'))
self.mock_dependencies(x)
x.is_member_of('test_group')
當我調用x.is_member_of()
, x.is_member_of()
無法按預期進行。
您可以在Python中訪問private屬性,因為private和protected是按慣例進行的。 -您正在尋找的基本上是使用_ClassName__private_attribute_name
因為python會執行重命名以實現約定的約定。
示例(返回MagicMock):
with mock.patch.object(Class, '_ClassName__private_attribute_name', return_value='value') as obj_mock:
pass
示例(返回原始值):
with mock.patch.object(Class, '_ClassName__private_attribute_name', new_callable=PropertyMock) as obj_mock:
obj_mock.return_value = 'string value'
Class
是對類本身的引用,而不是對實例的引用。
完整的例子:
from unittest.mock import patch, PropertyMock
from unittest import TestCase, main
class Private:
__attr = 'hello'
class PrivateTest(TestCase):
@patch.object(Private, '_Private__attr', new_callable=PropertyMock)
def test_private_attribute_value_change_decorator_success(self, private_mock):
obj = Private()
private_mock.return_value = 'string'
self.assertEqual('string', obj._Private__attr)
def test_private_attribute_value_change_context_manager_success(self):
with patch.object(Private, '_Private__attr', new_callable=PropertyMock) as o_mock:
obj = Private()
o_mock.return_value = 'mocked value'
self.assertEqual('mocked value', obj._Private__attr)
if __name__ == '__main__':
main()
對您的示例的修改:
from unittest import TestCase, mock, main
class A:
__user_id = 3
def __init__(self, user, group):
"""
Your logic is missing - obviously
:param user:
:param group:
"""
def __get_group_members(self):
"""
Your logic is missing - obviously
:return:
"""
return ['user_1', 'user_2']
def is_member_of(self, group_name):
members = self.__get_group_members(group_name)
# will return if the user is a member of the group
return self.__user_id in members
class GroupTest(TestCase):
group_data = [1, 2]
user_id = 'test_user_id'
@mock.patch.object(A, '_A__get_group_members')
@mock.patch.object(A, '_A__user_id', new_callable=mock.PropertyMock)
def test_this_is_my_first_success(self, user_id_mock: mock.PropertyMock, get_group_members_mock: mock.MagicMock):
get_group_members_mock.return_value = self.group_data
user_id_mock.return_value = 3
x = A('user_3', 'this_group')
self.assertEqual(False, x.is_member_of('test_group'))
@mock.patch.object(A, '_A__get_group_members')
@mock.patch.object(A, '_A__user_id', new_callable=mock.PropertyMock)
def test_this_is_my_first_failure(self, user_id_mock: mock.PropertyMock, get_group_members_mock: mock.MagicMock):
get_group_members_mock.return_value = self.group_data
user_id_mock.return_value = 1
x = A('user_1', 'this_group')
self.assertEqual(True, x.is_member_of('test_group'))
if __name__ == '__main__':
main()
如果您知道將在所有測試用例中模擬這兩個屬性,則可以在類級別添加裝飾器,並以同樣的方式期望參數。
如果通過__init__
或任何其他方法設置了屬性,則可以如下所示進行更改。
from unittest import TestCase, mock, main
class A:
def __init__(self, user, group):
"""
Your logic is missing - obviously
:param user:
:param group:
"""
def __get_group_members(self):
"""
Your logic is missing - obviously
:return:
"""
return ['user_1', 'user_2']
def is_member_of(self, group_name):
members = self.__get_group_members(group_name)
# will return if the user is a member of the group
return self.__user_id in members
class GroupTest(TestCase):
group_data = [1, 2]
user_id = 'test_user_id'
@mock.patch.object(A, '_A__get_group_members')
def test_this_is_my_first_success(self, get_group_members_mock: mock.MagicMock):
x = A('user_3', 'this_group')
x._A__user_id = 5
get_group_members_mock.return_value = self.group_data
self.assertEqual(False, x.is_member_of('test_group'))
@mock.patch.object(A, '_A__get_group_members')
def test_this_is_my_first_failure(self, get_group_members_mock: mock.MagicMock):
get_group_members_mock.return_value = self.group_data
x = A('user_1', 'this_group')
x._A__user_id = 1
self.assertEqual(True, x.is_member_of('test_group'))
if __name__ == '__main__':
main()
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