Python의 unittest로 경고가 발생했는지 테스트하는 방법은 무엇입니까?

Python의 unittest로 경고가 발생했는지 테스트하는 방법은 무엇입니까?

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Python에 다음 함수가 있으며 함수가 0을 인수로 가져 오면 경고가 발생하는지 unittest로 테스트하고 싶습니다. 나는 이미 assertRaises를 시도했지만 경고를 제기하지 않았기 때문에 작동하지 않습니다.

def isZero(i):
    if i != 0:
        print "OK"
    else:
        warning = Warning("the input is 0!") 
        print warning
    return i

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catch_warnings컨텍스트 관리자를 사용할 수 있습니다 . 기본적으로이를 통해 경고 처리기를 모의 처리하여 경고의 세부 정보를 확인할 수 있습니다. 자세한 설명과 샘플 테스트 코드 는 공식 문서 를 참조하십시오 .

import warnings

def fxn():
    warnings.warn("deprecated", DeprecationWarning)

with warnings.catch_warnings(record=True) as w:
    # Cause all warnings to always be triggered.
    warnings.simplefilter("always")
    # Trigger a warning.
    fxn()
    # Verify some things
    assert len(w) == 1
    assert issubclass(w[-1].category, DeprecationWarning)
    assert "deprecated" in str(w[-1].message)

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Python 3.2부터는 간단히 assertWarns()메소드 를 사용할 수 있습니다 .

with self.assertWarns(Warning):
    do_something()

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catch_warnings 컨텍스트를 캡슐화하기 위해 자신의 assertWarns 함수를 작성할 수 있습니다. 믹스 인을 사용하여 다음과 같은 방식으로 구현했습니다.

class WarningTestMixin(object):
    'A test which checks if the specified warning was raised'

    def assertWarns(self, warning, callable, *args, **kwds):
        with warnings.catch_warnings(record=True) as warning_list:
            warnings.simplefilter('always')

            result = callable(*args, **kwds)

            self.assertTrue(any(item.category == warning for item in warning_list))

사용 예 :

class SomeTest(WarningTestMixin, TestCase):
    'Your testcase'

    def test_something(self):
        self.assertWarns(
            UserWarning,
            your_function_which_issues_a_warning,
            5, 10, 'john', # args
            foo='bar'      # kwargs
        )

The test will pass if at least one of the warnings issued by your_function is of type UserWarning.

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@ire_and_curses' answer is quite useful and, I think, canonical. Here is another way to do the same thing. This one requires Michael Foord's excellent Mock library.

import unittest, warnings
from mock import patch_object

def isZero( i):
   if i != 0:
     print "OK"
   else:
     warnings.warn( "the input is 0!")
   return i

class Foo(unittest.TestCase):
    @patch_object(warnings, 'warn')
    def test_is_zero_raises_warning(self, mock_warn):
        isZero(0)
        self.assertTrue(mock_warn.called)

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

The nifty patch_object lets you mock out the warn method.

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One problem with the warnings.catch_warnings approach is that warnings produced in different tests can interact in strange ways through global state kept in __warningregistry__ attributes.

To address this, we should clear the __warningregistry__ attribute of every module before every test that checks warnings.

class MyTest(unittest.TestCase):

  def setUp(self):
    # The __warningregistry__'s need to be in a pristine state for tests
    # to work properly.
    for v in sys.modules.values():
      if getattr(v, '__warningregistry__', None):
        v.__warningregistry__ = {}

  def test_something(self):
    with warnings.catch_warnings(record=True) as w:
      warnings.simplefilter("always", MySpecialWarning)
      ...
      self.assertEqual(len(w), 1)
      self.assertIsInstance(w[0].message, MySpecialWarning)

This is how Python 3's assertWarns() method is implemented.

ReferenceURL : https://stackoverflow.com/questions/3892218/how-to-test-with-pythons-unittest-that-a-warning-has-been-thrown