Question

我正在尝试在以下业务代码中模拟Popen实例：

process = subprocess.Popen(command, stdout=subprocess.PIPE, shell=True)
output = process.communicate()[0]
if process.returncode != 0:

这是我的测试代码设置：

@mock.patch('subprocess.Popen.returncode')
@mock.patch('subprocess.Popen.communicate')
def testCommandExecutesCommunicate(self, mock_popen_communicate, mock_popen_returncode):

我也尝试过：

@mock.patch('subprocess.Popen.returncode')
@mock.patch('subprocess.Popen.communicate')
def testCommandExecutesCommunicate(self, mock_popen_communicate, mock_popen_returncode):

在两种情况下，我都无法使用returncode模拟

Error
Traceback (most recent call last):
  File "/Library/Frameworks/Python.framework/Versions/2.7/lib/python2.7/unittest/case.py", line 329, in run
    testMethod()
  File "/Library/Frameworks/Python.framework/Versions/2.7/lib/python2.7/site-packages/mock/mock.py", line 1297, in patched
    arg = patching.__enter__()
  File "/Library/Frameworks/Python.framework/Versions/2.7/lib/python2.7/site-packages/mock/mock.py", line 1369, in __enter__
    original, local = self.get_original()
  File "/Library/Frameworks/Python.framework/Versions/2.7/lib/python2.7/site-packages/mock/mock.py", line 1343, in get_original
    "%s does not have the attribute %r" % (target, name)
AttributeError: <class 'subprocess.Popen'> does not have the attribute 'returncode'

我应该如何模拟Popen？我应该以某种方式嘲笑Popen类吗？还是我通过模拟方法和属性走上了正确的轨道？

Answer 1

`AttributeError：没有属性'returncode'

查看位于subprocess.py的代码

class Popen():
    def __init__(self, ....):
        self.returncode = None

属性returncode由__init__设置，后来由communicate()等更新，类属性returncode不友好，会导致错误

为什么mockp.communicate（）mockp.communicate.return_value ='123'

mockp.communicate或与()相同，与mockp.communicate = mock.Mock()相同，这是一种为函数communicate创建新的模拟对象的方法

mock.communicate.return_value = list([2, 3])用于设置模拟函数的return_value。

解决方案：我对解决方案并不完全满意，但是我倾向于认为模拟整个类'Popen（）`是进行单元测试的方法。

对于单元测试，只需模拟整个类，模拟subprocess.Popen并设置returncode和communicate()并设置return_value，例如

remove_file.py

def do_cmd(command):
    process = subprocess.Popen(command, stdout=subprocess.PIPE, shell=True)
    exit_code = process.communicate()[0]
    return exit_code

test_remove_file.py

class TestDoCmd(unittest.TestCase):

    @mock.patch('remove_file.subprocess.Popen')
    def test_do_cmd(self, mockp):
        # add function
        mockp.returncode.return_value = 'abc'
        mockp.communicate()
        mockp.communicate.return_value = '123'
        file = '/tmp/none.txt'
        remove_file.do_cmd('rm -f {}'.format(file))
        mockp.assert_called_with('rm -f /tmp/none.txt', shell=True, stdout=-1)

Python：模拟属性还是模拟整个类？

1 个答案: