Question

我无法模拟接受** kwargs的函数。场景是我有ClassA（在我的具体情况下是我没写的东西），它有一个** kwargs的功能。 ClassB，它有一个ClassA实例，并调用** kwargs函数。我想通过模拟对A类功能的调用来测试ClassB。

这是我到目前为止所尝试的内容，在我的两次尝试中，我最终得到了一个TypeError。有没有办法做到这一点？我应该重新考虑另一个方面吗？

import unittest


#a class i have no control over. Has a function accepting **kwargs
class ClassA(object):

    def classFunctionAcceptingKwargs(self, **kwargs):
        return kwargs["a"] + kwargs["b"]

# a mock of the above class
class Mock_ClassA(object):

    def __init__(self):
        self.mockclassFunctionAcceptingKwargs = lambda **kwargs: None

    def classFunctionAcceptingKwargs(self, **kwargs):
        #FAILS: TypeError: mockFunctionAcceptingKwargs() takes exactly 0 arguments (1 given)
        return self.mockclassFunctionAcceptingKwargs(kwargs)
        #ALSO FAILS: TypeError: mockFunctionAcceptingKwargs() argument after ** must be a mapping, not set
        #return self.mockclassFunctionAcceptingKwargs(**{kwargs["a"] + kwargs["b"]})

#class B calls the class A kwargs but exposes a function with a dict
class ClassB(object):
    def __init__(self, classA):
        self.classA = classA

    def doSomething(self, dict):
        return self.classA.classFunctionAcceptingKwargs(**dict)

class TestClassA(unittest.TestCase):

    def runTest(self):
        a = ClassA()
        result = a.classFunctionAcceptingKwargs(**{"a":1, "b": 2})
        self.assertEqual(result, 3)

class TestClassB(unittest.TestCase):

    def runTest(self):

        mock = Mock_ClassA()
        def mockFunctionAcceptingKwargs(**kwargs):
            self.assertEqual(kwargs["a"], 1)
            self.assertEqual(kwargs["b"], 2)

        mock.mockclassFunctionAcceptingKwargs = mockFunctionAcceptingKwargs
        b = ClassB(mock)
        b.doSomething({"a": 1, "b": 2})

堆栈追踪：

Test Name:  TestClassB
Test Outcome:   Failed
Result StandardError:   
======================================================================
ERROR: runTest (module1.TestClassB)
----------------------------------------------------------------------
Traceback (most recent call last):
  File "C:\test\module1.py", line 49, in runTest
    b.doSomething({"a": 1, "b": 2})
  File "C:\test\module1.py", line 28, in doSomething
    return self.classA.classFunctionAcceptingKwargs(**dict)
  File "C:\test\module1.py", line 18, in classFunctionAcceptingKwargs
    return self.mockclassFunctionAcceptingKwargs(kwargs)
TypeError: mockFunctionAcceptingKwargs() takes exactly 0 arguments (1 given)
----------------------------------------------------------------------
Ran 1 test in 12.873s
FAILED (errors=1)

Answer 1

我不确定你为什么要打另一个功能。但是，如果必须具有实例属性mockclassFunctionAcceptingKwargs功能，那么只需使用kwargs传递**kwargs字典：

class Mock_ClassA(object):
    # ...
    def classFunctionAcceptingKwargs(self, **kwargs):
        return self.mockclassFunctionAcceptingKwargs(**kwargs)

如果你需要classFunctionAcceptingKwargs存在，你根本不需要调用那个lambda：

class Mock_ClassA(object):
    def __init__(self, mock_result):
        self.mock_result = mock_result
    def classFunctionAcceptingKwargs(self, **kwargs):
        self.called_with = kwargs
        return self.mock_result

然后只传递模拟的返回值，无论你需要传递回ClassB进行测试，然后你也可以检查是否传递了正确的值：

mock = Mock_ClassA(3)  # to return 3 back to the caller
b = ClassB(mock)
b.doSomething({"a": 1, "b": 2})
self.assertEqual(mock.called_with, {'a': 1, 'b': 2})

您可能希望使用unittest.mock library来构建模拟对象以进行传入（在Python 3中可用，并且可以安装用于Python 2的backport）。它会让你创建一个模拟的ClassA，然后使用API来测试模拟是否以预期的方式使用：

try:
    # Python 3
    from unittest import mock
except ImportError:
    # Python 2, backport
    import mock

class TestClassB(unittest.TestCase):
    def runTest(self):
        mockA = mock.Mock(spec=ClassA)  # only accept attributes ClassA also has
        mockA.classFunctionAcceptingKwargs.return_value = 3  # or whatever else you want it to return
        b = ClassB(mockA)
        b.doSomething({"a": 1, "b": 2})
        mockA.classFunctionAcceptingKwargs.assert_called_once_with(a=1, b=2)

使用unittest.mock作为模拟层进行演示：

>>> from unittest import mock
>>> class ClassA(object):
...     def classFunctionAcceptingKwargs(self, **kwargs):
...         return kwargs["a"] + kwargs["b"]
...
>>> class ClassB(object):
...     def __init__(self, classA):
...         self.classA = classA
...     def doSomething(self, dict):
...         return self.classA.classFunctionAcceptingKwargs(**dict)
...
>>> mockA = mock.Mock(spec=ClassA)
>>> mockA.classFunctionAcceptingKwargs.return_value = 3
>>> b = ClassB(mockA)
>>> b.doSomething({"a": 1, "b": 2})
3
>>> mockA.classFunctionAcceptingKwargs.assert_called_once_with(a=1, b=2)  # passes, no exception raised
>>> mockA.mock_calls
[call.classFunctionAcceptingKwargs(a=1, b=2)]

嘲笑一个接受** kwargs的函数

1 个答案: