[英]How to properly mock private members of a class
I am trying to write some unit tests for a method that depends on another private method. 我正在尝试为依赖于另一个私有方法的方法编写一些单元测试。 - As shown in the example below: -如下例所示:
def is_member_of(self, group_name):
members = self.__get_group_members(group_name)
The private method that I'd like to mock is __get_group_members
; 我想模拟的私有方法是__get_group_members
; I'd also like to mock the private attribute __user_id
since it will be used in the is_member_of
function (not shown in the example above). 我还想模拟私有属性__user_id
因为它将在is_member_of
函数中使用(在上面的示例中未显示)。
What I have so far: 到目前为止,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')
When I invoke x.is_member_of()
the mocking doesn't work as anticipated. 当我调用x.is_member_of()
, x.is_member_of()
无法按预期进行。
You can access a private attribute in Python since private and protected are by convention. 您可以在Python中访问private属性,因为private和protected是按惯例进行的。 - What you're looking for is basically using _ClassName__private_attribute_name
since, python carries out the renaming in order to achieve the convention agreed upon. -您正在寻找的基本上是使用_ClassName__private_attribute_name
因为python会执行重命名以实现约定的约定。
Example (returning a MagicMock): 示例(返回MagicMock):
with mock.patch.object(Class, '_ClassName__private_attribute_name', return_value='value') as obj_mock:
pass
Example (returning a raw value): 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
is a reference to the class itself - not the instance. Class
是对类本身的引用,而不是对实例的引用。
Complete Example: 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()
Modifications to your example: 对您的示例的修改:
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()
If you know you'll mock these two attributes in all test cases you can add the decorators on the class level and expect the arguments like-wise. 如果您知道将在所有测试用例中模拟这两个属性,则可以在类级别添加装饰器,并以同样的方式期望参数。
In the case where the attribute is set through the __init__
or any other method , you could simply alter it as shown below. 如果通过__init__
或任何其他方法设置了属性,则可以如下所示进行更改。
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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