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通过鼻子测试检查某个函数是否发出警告

发布于 2024-09-16 10:49:50 字数 176 浏览 7 评论 0原文

我正在使用 nose 编写单元测试，我想检查一下函数是否引发警告（该函数使用warnings.warn）。这是很容易就能做到的事情吗？

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染墨丶若流云 2024-09-23 10:49:50

def your_code():
    # ...
    warnings.warn("deprecated", DeprecationWarning)
    # ...

def your_test():
    with warnings.catch_warnings(record=True) as w:
        your_code()
        assert len(w) > 1

当然，您不仅可以检查长度，还可以深入检查：

assert str(w.args[0]) == "deprecated"

在 python 2.7 或更高版本中，您可以这样做最后一次检查为：

assert str(w[0].message[0]) == "deprecated"

def your_code():
    # ...
    warnings.warn("deprecated", DeprecationWarning)
    # ...

def your_test():
    with warnings.catch_warnings(record=True) as w:
        your_code()
        assert len(w) > 1

Instead of just checking the lenght, you can check it in-depth, of course:

assert str(w.args[0]) == "deprecated"

In python 2.7 or later, you can do this with the last check as:

assert str(w[0].message[0]) == "deprecated"

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娇纵 2024-09-23 10:49:50

有（至少）两种方法可以做到这一点。您可以在测试中的 warnings.WarningMessage 的 list 中捕获警告，或使用 mock 来patch 导入的内容模块中的警告。

我认为 patch 版本更通用。

raise_warning.py:

import warnings

def should_warn():
    warnings.warn('message', RuntimeWarning)
    print('didn\'t I warn you?')

raise_warning_tests.py:

import unittest
from mock import patch
import raise_warning

class TestWarnings(unittest.TestCase):

    @patch('raise_warning.warnings.warn')
    def test_patched(self, mock_warnings):
        """test with patched warnings"""
        raise_warning.should_warn()
        self.assertTrue(mock_warnings.called)

    def test_that_catches_warning(self):
        """test by catching warning"""
        with raise_warning.warnings.catch_warnings(True) as wrn:
            raise_warning.should_warn()
            # per-PEP8 check for empty sequences by their Truthiness 
            self.assertTrue(wrn)

There are (at least) two ways of doing this. You can catch the warning in the list of warnings.WarningMessages in test or use mock to patch the imported warnings in your module.

I think the patch version is more general.

raise_warning.py:

import warnings

def should_warn():
    warnings.warn('message', RuntimeWarning)
    print('didn\'t I warn you?')

raise_warning_tests.py:

import unittest
from mock import patch
import raise_warning

class TestWarnings(unittest.TestCase):

    @patch('raise_warning.warnings.warn')
    def test_patched(self, mock_warnings):
        """test with patched warnings"""
        raise_warning.should_warn()
        self.assertTrue(mock_warnings.called)

    def test_that_catches_warning(self):
        """test by catching warning"""
        with raise_warning.warnings.catch_warnings(True) as wrn:
            raise_warning.should_warn()
            # per-PEP8 check for empty sequences by their Truthiness 
            self.assertTrue(wrn)

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