Python 单元测试：使 AssertionError 成为错误而不是失败

Question

To make migrating existing test suites easier, unittest supports tests raising AssertionError to indicate test failure. However, it is recommended that you use the explicit TestCase.fail*() and TestCase.assert*() methods instead, as future versions of unittest may treat AssertionError differently.

我在测试代码中使用了很多 assert 语句，但这些断言的失败实际上应该是测试错误（即 "code did not run properly with those inputs"）而不是失败（即 "code gave incorrect output").

我可以看到以下可能的解决方案：

重写测试代码以抛出更好类型的异常
将除测试断言本身 (self.assertSomething(...)) 之外的所有测试方法包装在 try...except AssertionError: raise SomeOtherException 块中
更改单元测试的行为，使其考虑这些错误而不是失败。

选项 1 会花费一些时间，选项 2 感觉很老套；选项 3 对我来说是最好的，但它可用吗？（以防万一：不，我不能切换到 Python 3.）我在网上看不到任何东西，但很难使用特定的关键字。

MWE：

import unittest


def add_one_to_int(a):
    assert isinstance(a, int)
    return a + 1


class TestAddOne(unittest.TestCase):
    def test_one_plus_one_is_three(self):
        # This tests fails with
        #   AssertionError: 2 != 3
        # which is fine
        self.assertEqual(add_one_to_int(1), 3)  

    def test_add_one_to_str(self):
        # This tests fails with
        #   AssertionError
        # when I would rather have it an error
        add_one_to_int('some string')

if __name__ == '__main__':
    unittest.main(verbosity=2)  # 2 failures instead of 1 failure, 1 error

Answer 1

我认为选项 3 可以通过 class 属性 "failureException" 实现，正如 Python 2.7:

的单元测试文档中所定义的

failureException: This class attribute gives the exception raised by the test method. If a test framework needs to use a specialized exception, possibly to carry additional information, it must subclass this exception in order to “play fair” with the framework. The initial value of this attribute is AssertionError.

例如：

import unittest

class MyException(Exception): 
    pass

class MyUnitTest(unittest.TestCase):
    failureException = MyException

def add_one_to_int(a):
    assert isinstance(a, int)
    return a + 1


class TestAddOne(MyUnitTest):  # <--------- See above
    def test_one_plus_one_is_three(self):
        # This tests fails with
        #   AssertionError: 2 != 3
        # which is fine
        self.assertEqual(add_one_to_int(1), 3)  

    def test_add_one_to_str(self):
        # This tests fails with
        #   AssertionError
        # when I would rather have it an error
        add_one_to_int('some string')

if __name__ == '__main__':
    unittest.main(verbosity=2)  # ------> FAILED (failures=1, errors=1)

Python 单元测试：使 AssertionError 成为错误而不是失败

Python unittest: make AssertionError an error instead of a failure

python

python-unittest