python - 无法模拟从另一个类继承的类(创建/使用单例对象)

Question

我有三个类和一个单元测试用例:
1)A.py:

class A(object):
    def __new__(cls):
        """
         Overriding the __new__ method to make the A a singleTon class
         :return: cls.instance
         """
        if not hasattr(cls, 'instance') or not cls.instance:
             cls.instance = super(A, cls).__new__(cls)
             return cls.instance
        def execute():
             print("class A")
             return "Coming from class A"

2)B.py:

from A import A
class B(object):
    def __init__(self):
        """
         Initialize and declare any members/methods that can be passed over class that inherit this class
        """
        self.a = A()
        self.name = Name()
    def run(self):
        pass

class Name:
    def __init__(self):
        self.test_dict = {}

3) C.py

from B import B
class C(B):
    def __init__(self):
        super(C, self).__init__()
        self.result = None

    def run(self):
        self.result = self.A.execute()
        return self.result

4) 测试.py

import unittest
from unittest.mock import patch
from A import A
from B import B
from C import C

class TestMethods(unittest.TestCase):

    @patch('A.A')
    def test_basic(self, MockA):
        a = MockA()
        a.execute.return_value = "Testing code"

        c = C()
        result = c.run()
        self.assertEqual(result,"Testing code")

if __name__ == '__main__':
    unittest.main()

在执行 test.py 时，出现以下错误:

错误:test_basic ( 主 .TestMethods)

Traceback (most recent call last):

File "C:\Users\davinder\AppData\Local\Continuum\Anaconda3\lib\unittest\mock.py", line 1179, in patched
   return func(*args, **keywargs)
File "C:/Users/davinder/PythonCodes/Test Framework/test.py", line 14, in test_basic
   c = C()
File "C:\Users\davinder\PythonCodes\Test Framework\C.py", line 5, in __init__
   super(C, self).__init__()
 File "C:\Users\davinder\PythonCodes\Test Framework\B.py", line 8, in __init__
    self.a = A()
 File "C:\Users\davinder\PythonCodes\Test Framework\A.py", line 8, in __new__
    cls.instance = super(A, cls).__new__(cls)
 TypeError: super() argument 1 must be type, not MagicMock

 ----------------------------------------------------------------------
 Ran 1 tests in 0.018s

 FAILED (errors=1)

我想通过使用 test.py 中使用的不同返回值(通过修补)来测试 C.py 类中的 run()。
提前感谢您的帮助

编辑:即使我在 test.py 中模拟 C，像这样:

import unittest
from unittest.mock import patch
from A import A
from B import B
from C import C
from B import Name

class TestMethods(unittest.TestCase):

    @patch('C.C')
    @patch('A.A')
    def test_basic(self, MockA, MockC):
        a1 = MockA()
        a1.execute.return_value = "Testing code"

        c = MockC()
        c.a = a1
        c.name = Name()

        result = c.run()
        self.assertEqual(result,"Testing code")

 if __name__ == '__main__':
     unittest.main()

收到此错误:

FAIL: test_basic (__main__.TestMethods)
----------------------------------------------------------------------
Traceback (most recent call last):
    File "C:\Users\davinder\AppData\Local\Continuum\Anaconda3\lib\unittest\mock.py", line 1179, in patched
        return func(*args, **keywargs)
    File "C:/Users/davinder/PythonCodes/Test Framework/test.py", line 22, in test_basic
        self.assertEqual(result,"Testing code")
 AssertionError: <MagicMock name='C().run()' id='2464384921272'> != 'Testing code'

 ----------------------------------------------------------------------
 Ran 1 tests in 0.018s

 FAILED (failures=1)

Answer 1

我不得不在 B.py 中更改您的导入成为 import而不是 from .错误是因为 A正在从 B 上查找模块，所以你的补丁必须是 @patch('B.A') .无论如何，这是有关该主题的有用阅读:http://www.voidspace.org.uk/python/mock/patch.html#where-to-patch

现在，这是更改后的代码:

"""test.py"""
import unittest
from unittest.mock import patch
from c_module import C

class TestMethods(unittest.TestCase):
    @patch('b_module.A')
    def test_basic(self, mock_a):
        mock_a.return_value.execute.return_value = "Testing code"
        c = C()
        result = c.run()
        self.assertEqual(result,"Testing code")

if __name__ == '__main__':
    unittest.main()

"""c_module.py"""
from b_module import B
class C(B):
    def __init__(self):
        super(C, self).__init__()
        self.result = None
    def run(self):
        self.result = self.a.execute()
        return self.result

"""b_module.py"""
from a_module import A
class B(object):
    def __init__(self):
        """
         Initialize and declare any members/methods that can be passed over class that inherit this class
        """
        self.a = A()
        self.name = Name()
    def run(self):
        pass

class Name:
    def __init__(self):
        self.test_dict = {}

"""a_module.py"""
class A(object):
    def __new__(cls):
        """
         Overriding the __new__ method to make the A a singleTon class
         :return: cls.instance
         """
        if not hasattr(cls, 'instance') or not cls.instance:
             cls.instance = super(A, cls).__new__(cls)
             return cls.instance
        def execute():
             print("class A")
             return "Coming from class A"

我还鼓励您更改模块命名。在处理此问题时，很难不将模块与类混为一谈。您可以在上面看到我已将模块名称更改为蛇形大小写并将类保留原样。