Python :模拟一个属性还是模拟整个类？
Python :模拟一个属性还是模拟整个类？
提问于 2018-07-28 01:11:46
我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):在这两种情况下，我都会收到returncode模拟的错误
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？我应该以某种方式模仿Popen类吗？或者，通过模拟方法+属性，我走上了正确的道路？
回答 1
Stack Overflow用户
发布于 2018-07-28 06:17:03
` `AttributeError:没有'returncode‘属性
看看subprocess.py上的代码，
class Popen():
def __init__(self, ....):
self.returncode = None属性returncode由__init__设置，然后由communicate()等更新，类属性returncode不是模拟友好的，因此会导致错误
为什么mockp.communicate() mockp.communicate.return_value = '123‘
mockp.communicate或with ()与mockp.communicate = mock.Mock()相同，后者是为函数communicate创建新模拟对象的一种方式
mock.communicate.return_value = list([2, 3])用于设置模拟函数的return_value。
解决方案:我对这个解决方案并不完全满意，但我倾向于认为mock整个类的‘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，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_codetest_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)页面原文内容由Stack Overflow提供。腾讯云小微IT领域专用引擎提供翻译支持
原文链接：
https://stackoverflow.com/questions/51562651
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